JPH11298243A - Current control circuit and frequency generation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current control circuit which outputs a current following the variance of a low frequency and can suppress the output of the current following the variance of a high frequency by controlling a collector current and outputting a current in accordance with the collector current. SOLUTION: A current control circuit 51 constitutes a low band pass filter, LPF and a minute current ΔI corresponding to only the variance of a low frequency is obtained among the variances of a power supply voltage Vcc according to the set value of cut-off frequency of the LPF. The circuit 51 outputs a current following the variance of a low frequency if the voltage Vcc varies at a low frequency level and can suppress the output of a current following the variance of a high frequency if the high frequency noises are mixed into the voltage Vcc to vary at the high frequency. Therefore, if the noises are mixed into the voltage Vcc at a specific frequency level, the cut-off frequency is set to attenuate the noises and the constants can be set for resistance elements R1 and R2 and a capacitor C, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency generating circuit for generating an oscillating signal of a predetermined frequency, which is used, for example, in a television or radio tuner. The present invention relates to a current adjustment circuit that outputs a current according to a power supply voltage.

[0002]

2. Description of the Related Art FIG. 1 is a circuit diagram showing an example of an oscillation circuit using a differential pair of transistors. This oscillation circuit 10
0, the power supply voltage the collector of one transistor Q ₁₁ to the supply terminal T _v of Vcc is connected via a resistor element R _10, supply terminal T _v the other transistor Q of the power supply voltage Vcc
Is connected to the collector of _12, connection point NQ between the emitters is grounded via the current source I _10, a bias voltage is supplied is supplied through a constant voltage are each resistive element R _11, R ₁₂ in each base Transistors Q ₁₁ , Q
_12, a first capacitor C ₁₁ having one end connected to the collector of one transistor Q _11, the other transistor Q
One end connected to the _12-based, a second capacitor C ₁₂ whose other end is connected to the other end of the first capacitor C _11,
And a resonant circuit connected to the other end of the first capacitor C _11.

[0003] resonance circuit is configured to inductor L ₁₃ and capacitor C ₁₃ connected in parallel. Node N27 is connected to one end of the inductor L _13, is connected to one end of the capacitor C _13, is connected to the node N26. Node N
28 is connected to the other end of the inductor L _13, a capacitor C
₁₃ is connected to the other end and grounded. Symbol GND indicates a ground potential.

[0004] One end of the capacitor C ₁₁ is connected to the terminal T _0, one end of the capacitor C ₁₂ is connected to the terminal T _1. The terminals T ₀ and T ₁ constitute output terminals for outputting an oscillation signal. The other end of the capacitor C ₁₁ is connected to the node N26, the other end of the capacitor C ₁₂ is connected to the node N26.

[0005] node N22 is connected to the supply terminal T _V power supply voltage Vcc, is connected to the collector of the npn-type transistor Q _12. Resistive element R ₁₀ between the nodes N22 and N23 are connected. Node N23 is connected to the terminal T _0, and is connected to the collector of the npn-type transistor Q _11. Node N24 is connected to the terminal T _1, and is connected to the base of the npn transistor Q _12. The base of transistor Q ₁₁ is connected to the node N25 via a resistance element R _11. Between node N25 and node N24, the resistance element R ₁₂ is connected. The node N25 is connected to the constant voltage source E and is supplied with a constant voltage.

A semiconductor integrated circuit (IC: Integrated Circuit)
it) 110 includes resistance elements R ₁₀ , R ₁₁ , R ₁₂ , transistors Q ₁₁ , Q _{12 of} a differential pair, a current source I _10, and a constant voltage source E
And Current source I ₁₀ can be a resistor element. Capacitors C ₁₁ , C ₁₂ , C ₁₃ and inductor L
_Reference numeral ₁₃ is externally attached to the semiconductor integrated circuit 110, and the externally attached portion is indicated by reference numeral 120.

[0007] oscillation frequency of the oscillation signal of the oscillation circuit 100 is determined by the resonant frequency of the resonant circuit inductor L ₁₃ and capacitor C ₁₃ connected in parallel. Also,
Is determined by the base input capacitance Cπ such parasitic capacitance and the transistor Q _11, Q ₁₂ of the transistors Q _11, Q ₁₂ of the oscillation circuit 100, hereinafter, the total capacity of the transistor Q _11, Q ₁₂ and Cp. The base input capacitance Cπ is determined by the emitter currents of Q ₁₁ and Q ₁₂ .

Since the total capacitance Cp also depends on the collector-emitter voltage Vce of the transistor, if the power supply voltage Vcc fluctuates, the collector-emitter voltage Vce fluctuates, and the total capacitance Cp fluctuates. Normally, when the power supply voltage Vcc increases, the total capacitance Cp decreases, and the oscillation frequency increases. on the other hand,
When the power supply voltage Vcc decreases, the total capacitance Cp increases, and the oscillation frequency decreases.

FIG. 2 is a circuit diagram of a frequency generation circuit 200 having a current adjustment circuit 50. This frequency generation circuit 2
00, the node N20 is connected to the connection point NQ between the emitters of the transistors Q ₁₁ and Q ₁₂ of the differential pair,
The output terminal T _C0 of the current adjustment circuit 50 is connected to 20.

In the current adjusting circuit 50, the power supply voltage Vcc is input from the input terminal T _V0 , and the power supply voltage Vcc is divided into the voltage dividing resistors R _B1 ,
Divided by R _B2, the dividing resistors R _B1, the connection point of R _B2 NB base of the npn-type transistor Q ₁₇ is connected. The emitter of the transistor Q ₁₇ is grounded through a resistor R _17, the collector is connected to the output terminal T _C0. In the frequency generation circuit 200 of FIG. 2, the same components of the oscillation circuit 220 as those of the oscillation circuit 100 of FIG. 1 are denoted by the same reference numerals, and the description of the same components will be omitted.

The frequency generation circuit 200 has a semiconductor integrated circuit 210 and an external part 120. The frequency generation circuit 200 has a current adjustment circuit 50 and an oscillation circuit 220 in the circuit configuration. The semiconductor integrated circuit 210 includes a current regulating circuit 50, a resistance element _{R 10, R 11, R 12} , and transistors Q _11, Q ₁₂ of the differential pair, a current source I _10, and a constant voltage source E. The node N21 is connected to a supply terminal T of the power supply voltage Vcc.
_V , the node N22, and the input terminal T _V0 .

When the power supply voltage Vcc rises, the collector current I
_{As c} increases, the current flowing through the Q ₁₁ and Q ₁₂ emitters increases, and the base input capacitance Cπ increases. In this way,
A decrease in the total capacitance Cp when the power supply voltage Vcc rises can be suppressed. When lowering the power supply voltage Vcc is Q _11, Q ₁₂ emitter current is reduced to decrease the collector current I _c is the base input capacitance Cπ is reduced. In this manner, an increase in the total capacitance Cp when the power supply voltage Vcc falls can be suppressed.

FIG. 3 is a frequency characteristic diagram obtained by frequency-analyzing the output signal of the frequency generation circuit of FIG. The horizontal axis is frequency f
And the vertical axis indicates the level L. The first sides of the peak frequency f ₁ is the design value of the oscillation frequency, the high frequency noise caused by the second peak frequency f ₂ and the third peak frequency f ₃ has appeared. In the frequency characteristic diagram of FIG. 3, the interval between the frequencies f ₁ , f ₂ and f ₃ is the frequency f _{NS of the} high-frequency noise.
be equivalent to.

[0014]

In the frequency generator of Figure 2 [0008], when high frequency noise is mixed to the power supply voltage Vcc, and the collector current I _c is varied in accordance with the high-frequency noise, noise in the output signal of the oscillation circuit 220 There is a problem that it appears as a component. That is, in the frequency generation circuit of FIG. 2, fluctuation of the oscillation frequency due to fluctuation of the low frequency of the power supply voltage Vcc can be suppressed, but when high frequency noise is mixed in the power supply voltage Vcc, high frequency noise is mixed in the oscillation signal. , There is a problem.

An object of the present invention is to output a current following a low-frequency fluctuation when a power supply voltage fluctuates at a low frequency, and to output a current at a high frequency when high-frequency noise is mixed in the power supply voltage. Another object of the present invention is to provide a current adjustment circuit capable of suppressing the output of a current following the fluctuation of the high frequency. An object of the present invention is to suppress fluctuations in the oscillation frequency due to fluctuations in the low frequency of the power supply voltage,
An object of the present invention is to provide a frequency generation circuit that can prevent high frequency noise from being mixed in an oscillation signal when high frequency noise is mixed in a power supply voltage.

[0016]

In the current adjusting circuit according to the present invention, the emitters are connected to each other through a resistance element, a voltage proportional to the power supply voltage is supplied to the base of one transistor, and the base of the other transistor is supplied. Is supplied with a constant voltage, and both emitters are respectively connected to the ground via a current source. A transistor of the first differential pair is connected to the collector of the one transistor, and the collector is connected to the power supply voltage. A first transistor connected to a supply terminal, a second transistor having an emitter connected to the collector of the other transistor, and a collector connected to a supply terminal for the power supply voltage; and a base connected to the base of the first transistor. A capacitor having one end connected thereto and the other end connected to the base of the second transistor, and one end connected to the one end of the capacitor; The base of the transistor is connected, the base of the other transistor is connected to the other end, the emitters are connected to each other via a resistance element, and both emitters are connected to the supply terminal of the power supply voltage via current sources. A second differential pair of transistors, a current mirror circuit connected to both collectors of the second differential pair of transistors to control both collector currents, and outputs a current corresponding to the collector current Output circuit.

In the current adjusting circuit according to the present invention, preferably, in the output circuit, an anode is connected to a collector of the one of the transistors of the second differential pair, and a cathode is connected via a resistance element. A grounded diode, a constant current source that outputs a constant current to the anode, a third transistor having a base connected to the anode, an emitter grounded via a resistor, and a collector of the third transistor. And an output terminal connected to the output terminal.

In the frequency generation circuit according to the present invention, the collector of one transistor is connected to the supply terminal of the power supply voltage via the resistance element, the collector of the other transistor is connected to the supply terminal of the power supply voltage, and the emitters are connected to each other. A connection point is grounded via a current source, a constant voltage is supplied to each base via a resistance element, and a bias voltage is supplied to each base. A first capacitor having one end connected to the collector of one transistor, one end connected to the base of the other transistor of the differential pair of transistors, and the other end connected to the other end of the first capacitor; An oscillation circuit having a second capacitor and a resonance circuit connected to the other end of the first capacitor; And are connected, the base of one transistor is supplied a voltage proportional to the power supply voltage,
A constant voltage is supplied to the base of the other transistor,
A first differential pair of transistors, both emitters of which are grounded via a current source, respectively, and an emitter is connected to a collector of the one of the transistors of the first differential pair, and the collector is A first transistor connected to a power supply voltage supply terminal, an emitter connected to a collector of the other transistor of the first differential pair of transistors, and a collector connected to the power supply voltage supply terminal; A second transistor, a capacitor having one end connected to the base of the first transistor and the other end connected to the base of the second transistor;
The base of one transistor is connected to the one end of the capacitor, the base of the other transistor is connected to the other end, the emitters are connected via a resistance element,
A second differential pair of transistors, both emitters of which are connected to a supply terminal of the power supply voltage via a current source, and both emitters of which are connected to both collectors of the second differential pair of transistors, respectively. A current mirror circuit for controlling a collector current; and an output circuit for outputting a current corresponding to the collector current to a connection point between the emitters of the oscillation circuit. An output terminal for outputting an oscillation signal is connected to the one end or the one end of the second capacitor.

In the frequency generation circuit of the present invention, preferably,
The output circuit includes a diode having an anode connected to a collector of the one of the transistors of the second differential pair, and a cathode having a cathode grounded via a resistance element, and a constant current for outputting a constant current to the anode. A current source; and a third transistor having a base connected to the anode, an emitter grounded via a resistor, and a collector connected to a connection point between the emitters of the oscillation circuit.

In the current adjusting circuit according to the present invention, when the power supply voltage fluctuates minutely, the resistance element connected between the emitters of the transistors of the first differential pair supplies a minute current proportional to the minute voltage due to the minute fluctuation of the power supply voltage. Flows. This minute current minutely changes the base current of the first transistor and the second transistor, and a minute voltage due to the minute current is generated between the terminals of the capacitor of the current adjustment circuit. The minute voltage generated between the terminals of the capacitor causes a minute current to flow through the resistance element connected between the emitters of the transistors of the second differential pair. A current proportional to the minute current is output by the current mirror circuit from a connection point between the collector of the first transistor of the second differential pair of transistors and the current mirror circuit.

In the current adjusting circuit according to the present invention, the anode of the transistor of the second differential pair is connected to the collector of one of the transistors, and the cathode is connected to the ground through a resistor. A constant current source for outputting a current, a third transistor having a base connected to the anode, an emitter grounded via a resistor, and an output terminal connected to a collector of the third transistor; A current mirror circuit is formed by the diode, the resistance element connected to the diode, and the third transistor and the resistance element connected to the third transistor, and a current equal to the current flowing into the anode of the diode is generated by the current mirror circuit. 3 occurs at the collector of the transistor.

[0022]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 4 is a circuit diagram showing an example of the current adjustment circuit according to the present invention.

[0023] In the current regulating circuit 51, is connected emitters each other via the resistance element R _1, the base of one transistor Q ₁ is supplied a voltage V _N0 proportional to the power supply voltage Vcc, and the other transistor Q ₂ The base of the first differential pair of transistors Q ₁ and Q ₂ whose emitters are grounded via current sources I _Q1 and I _Q2 , respectively, and the one transistor Q ₁ the collector emitter connected to a first transistor Q ₃ whose collector is connected to the input terminal T _V0 of the power supply voltage Vcc,
Emitter connected to the collector of the other transistor Q _2, the second transistor Q ₄ whose collector is connected to the input terminal T _V0 of the power supply voltage Vcc, one end to the base of the first transistor Q ₃ connected is a capacitor C whose other end is connected to the base of the second transistor Q _4, one transistor-based P ₁ to said one end of the capacitor C is connected, the other transistor P ₂ on the other end The base is connected and the emitters are connected to the resistance element R
₂ and a second differential pair of transistors P ₁ , P ₂ whose emitters are connected to the input terminal T _V0 of the power supply voltage Vcc via current sources I _P1 , I _P2 , respectively.
A current mirror circuit connected to both collectors of the transistors P ₁ and P ₂ of the second differential pair for controlling both collector currents, and an output circuit 55 for outputting a current corresponding to the collector currents. Have.

The output circuit 55, transistor P ₁ of the one of the transistors P _1, P ₂ of the second differential pair
A diode D1 whose anode is connected to a collector of the same and a cathode is grounded via a resistance element R _D1 , a constant current source I _D1 that outputs a constant current I to the anode, a base is connected to the anode, and an emitter is connected It has a third transistor Q ₇ grounded via a resistance element R _Q7 , and an output terminal T _C0 connected to the collector of the third transistor Q ₇ . A constant voltage is supplied to each base of the transistors P ₁ and P ₂ of the second differential pair via resistance elements R ₃₁ and R ₃₂ having the same resistance value, and a bias voltage is supplied.

The structure of the current adjusting circuit 51 will be described in more detail. Input terminals T _V0 of the power supply voltage Vcc are connected to nodes N10, N11, N12, N13,
N14 and N15 are connected. The resistance element R ₀ is connected between the node N 10 and the node N _0, and the node N ₀ is grounded via the current source I ₀ . Sign GND
Indicates a ground potential. Node N0 is connected to the base of the transistor Q _1.

The emitter of the transistor Q ₁ is connected to the current source I
_Grounded via _Q1 . The emitter of the transistor Q ₂ is grounded via the current source I _Q2. The emitter of the transistors Q _1, transistor Q ₂ is connected through a resistor R _1. The collector of the transistor Q ₁ is connected to the emitter of the transistor Q _3. The collector of the transistor Q ₂ is connected to the emitter of the transistor Q _4, the base of the transistor Q ₂ is has a constant voltage is supplied from a constant voltage source E _2.

[0027] The base of the transistor Q ₃ is connected to the node N1, and the collector is connected to the node N11.
Base of the transistor Q ₄ is connected to the node N2, the collector is connected to the node N12. The capacitor C is connected between the node N1 and the node N2. Node N1 is connected to the base of transistor P _1, the node N2 is connected to the base of the transistor P _2. Characteristics of the transistor Q ₃ and the transistor Q ₄ are the same.

The emitter of the transistor P ₂ is a current source I _P2
Connected to the node N13 via the emitter of the transistor P ₁ is connected to the node N14 via a current source I _P1. Emitters of the transistors P ₁ and transistor P ₂ is connected through the resistance element R _2. Is the resistance element R ₃₂ is connected between the node N2 and a node N16, which is connected resistive element R ₃₁ between the nodes N3 and N16, the node N16 is connected to a constant voltage source E _1. Node N3 is connected to node N1.

[0029] to the collector of the transistor P ₂ is node N
5 is connected to the collector of the transistor P ₁ is connected to a node N6. The collector of the transistor Q ₅ is connected to the node N5, the base is connected to the node N7, the node N5 and a node N7 are connected. The emitter of the transistor Q ₅ is grounded via the resistor R _Q5. The base of transistor Q ₆ is connected to the node N7, the emitter is grounded through a resistor R _Q6.

The node ND is connected to the node N6, the anode of the diode D1 is connected to the node ND, and the cathode of the diode D1 is grounded via the resistor _RD1 . Node ND is connected to node N15 via constant current source _ID1 . Node ND is transistor Q
₇ and the emitter is grounded via a resistor _RQ7 . The collector of the transistor Q ₇ is connected to the output terminal T _C0. The magnitude of the drive current of the current source I _Q1, I _Q2 are the same, the magnitude of the drive current of the current source I _P1, I _P2 is the same, the resistance value of the resistance element R _Q5, R _Q6 are the same , And the resistance values of the resistance elements R _D1 and R _Q7 are the same.

The connection point between the resistor R ₀ and the current source I ₀ N0
Is a voltage obtained by dividing the power supply voltage Vcc, that is, the power supply voltage Vcc.
A voltage V _N0 proportional to cc is generated. The minute voltage ΔV is a variation of the potential V _{N0 at} the connection point N0. When the power supply voltage Vcc fluctuates, the potential V _N0 of the connection point N0 fluctuates, and the minute voltage △
V results. This small voltage △ V is applied to the base of the transistor Q _1. This minute voltage ΔV is equal to the resistance element R ₁
And a minute current of ΔI ₁ = △ V / r ₁ flows through the resistance element R ₁ . Here, the resistance value of the resistance element R ₁ is r ₁
Expressed by

[0032] Then, a minute current ΔI _1, which corresponds to the increase of the collector current of the npn transistor Q ₁ is generated. Further, a small current ΔI ₁ corresponding to the decrease of the collector current of npn transistor Q ₂ is generated.

Then, a small current ΔI ₂ corresponding to the increase in the base current of the transistor Q ₃ is generated. ΔI ₂ =
ΔI ₁ / h _fe . Further, a small current ΔI ₃ corresponding to the decrease of the base current of the transistor Q ₄ is generated.
ΔI ₃ = ΔI ₁ / h _fe . Small currents ΔI ₂ and ΔI _{3
Are the} same size, and h _fe is the current amplification factor of the transistors Q ₃ and Q ₄ .

The minute voltage ΔV ₂ is generated in the capacitor C by the minute currents ΔI ₂ and ΔI ₃ . ΔV ₂ = ΔI ₂ /
2ωC ₀ . Here, the capacitance of the capacitor C is C ₀ , ω = 2πf, and f is the minute voltage ΔV
Is the frequency that fluctuates.

The small voltage [Delta] V ₂ is applied to the resistance element R _2, the resistance element R ₂ flows a small current [Delta] I _4. ΔI ₄
= ΔV ₂ / r ₂ = ΔI ₂ / (2ωC ₀ × r ₂ ).
Here, it represents the resistance value of the resistance element R ₂ and r _2.

Then, a small current ΔI ₅ corresponding to the increase in the collector current of the pnp transistor P ₁ is generated. Further, a small current ΔI ₄ corresponding to the decrease of the collector current of the pnp transistor P ₂ is generated. The small currents ΔI ₄ and ΔI ₅ have the same magnitude.

On the other hand, a current mirror circuit is formed by npn-type transistors Q ₅ and Q ₆ and resistance elements R _Q5 and R _Q6 , and generates a small current ΔI ₆ corresponding to a decrease in the collector current of transistor Q _6. . Small current ΔI
₆ and ΔI ₄ are the same size.

Then, a small current .DELTA.I flows from node N6 to node ND. ΔI = ΔI ₅ + ΔI ₆ = 2 × ΔI ₄
= ΔI ₂ / (ωC ₀ × r ₂ ) = ΔV / (ωC ₀ × r ₂ ×
r ₁ × h _fe ).

The addition current I + Δ of the constant current I from the constant current source _ID1 and the minute current ΔI is connected to the anode of the diode D1.
I flows. A diode D1 and a resistance element _RD1 ,
an npn-type transistors Q ₇ and resistance element R _Q7 is constituted by the current mirror circuit, the collector current I
+ ΔI will flow.

ΔI = ΔV / (ωC ₀ × r ₂ × r ₁ ×
h _fe ), a small current ΔI proportional to the small voltage ΔV is obtained. When the frequency of the minute voltage ΔV is high, there is a term of ωC ₀ in the numerator of the equation, so
Becomes smaller. Therefore, the current adjusting circuit 51 forms a low-pass filter (low-pass filter).

With the set value of the cut-off frequency fc of the low-pass filter, it is possible to obtain a small current ΔI corresponding only to the change in the low frequency among the changes in the power supply voltage Vcc. In the current adjusting circuit 51, when the power supply voltage Vcc fluctuates at a low frequency, a current that follows the fluctuation of the low frequency can be output. Therefore, the output of the current following the fluctuation of the high frequency can be suppressed. Therefore,
If noise is mixed in the power supply voltage Vcc at a specific frequency, a cutoff frequency for attenuating the noise may be set, and the respective element constants of the resistance elements R ₁ and R ₂ and the capacitor C may be set.

In order to set the cutoff frequency low, the element constants r ₁ , r ₂ and C ₀ of the resistance elements R ₁ and R ₂ and the capacitor C may be increased. Increasing the capacitance C _{0 of the} capacitor C is not preferable because a large electrode plate area is required on the IC chip when the current adjustment circuit 51 is formed on the IC chip. On the other hand, there is a term of h _fe in the numerator of the equation, and the current amplification factor h _fe is
Since it can take a value of about 00, the cutoff frequency can be set low without increasing the capacitance C ₀ much as compared with the case of using a first-order RC low-pass filter composed of one resistive element and a capacitor. can do.

FIG. 5 shows that the oscillation circuit 220 includes the current adjustment circuit 5.
FIG. 2 is a circuit diagram of a frequency generation circuit 300 to which No. 1 is connected. In this frequency generation circuit 300, the differential pair of transistors Q
_11, the node N20 to the connection point NQ between the emitters of Q ₁₂ is connected, an output terminal T _C0 of the current regulating circuit 51 is connected to the node N20.

[0044] The oscillator circuit 220, the collector of one transistor Q ₁₁ to the supply terminal T _v of the power supply voltage Vcc is connected through the resistance element R _10, the power supply voltage Vcc supply terminal T _v the other transistor Q of is connected to the collector of _12, connection point NQ between the emitters is grounded via the current source I _10, each base respectively resistance element is constant voltage to the R _11, R
Transistor Q ₁₁ of the differential pair bias voltage is supplied is supplied via _12, and Q _12, a first capacitor C one end to the collector of one transistor Q ₁₁ is connected
_11, is connected to one end to the base of the other transistor Q _12, a second capacitor C ₁₂ whose other end is connected to the other end of the first capacitor C _11, the other end of the first capacitor C ₁₁ Connected to the resonance circuit.

The resonant circuit is configured to inductor L ₁₃ and capacitor C ₁₃ connected in parallel. Node N27 is connected to one end of the inductor L _13, is connected to one end of the capacitor C _13, is connected to the node N26. Node N
28 is connected to the other end of the inductor L _13, a capacitor C
₁₃ is connected to the other end and grounded.

[0046] One end of the capacitor C ₁₁ is connected to the terminal T _0, one end of the capacitor C ₁₂ is connected to the terminal T _1. The terminals T ₀ and T ₁ constitute output terminals for outputting an oscillation signal. The other end of the capacitor C ₁₁ is connected to the node N26, the other end of the capacitor C ₁₂ is connected to the node N26.

The node N22 is connected to the supply terminal T _V power supply voltage Vcc, is connected to the collector of the npn-type transistor Q _12. Resistive element R ₁₀ between the nodes N22 and N23 are connected. Node N23 is connected to the terminal T _0, and is connected to the collector of the npn-type transistor Q _11. Node N24 is connected to the terminal T _1, and is connected to the base of the npn transistor Q _12. The base of transistor Q ₁₁ is connected to the node N25 via a resistance element R _11. Between node N25 and node N24, the resistance element R ₁₂ is connected. The node N25 is connected to the constant voltage source E and is supplied with a constant voltage.

The frequency generation circuit 300 has a semiconductor integrated circuit 310 and an external part 120. The frequency generation circuit 300 has a current adjustment circuit 51 and an oscillation circuit 220 in the circuit configuration. The semiconductor integrated circuit 310 includes a current regulating circuit 51, a resistance element _{R 10, R 11, R 12} , and transistors Q _11, Q ₁₂ of the differential pair, a current source I _10, and a constant voltage source E. The node N21 is connected to a supply terminal T of the power supply voltage Vcc.
_V , the node N22, and the input terminal T _V0 .

The power at the time of rise of the voltage Vcc increases the emitter current of Q _11, Q ₁₂ current I _T is increased flowing into the output terminal T _C0 is base input capacitance of the transistor Q _11, Q ₁₂ of the differential pair Cπ Increase. Thus, the power supply voltage Vcc
Can be prevented from decreasing when the total capacitance Cp rises.

The power supply voltage during descent of Vcc decreases current I _T flowing into the output terminal T _C0 is Q _11, the emitter current of Q ₁₂ is reduced, the base input capacitance of the transistor Q _11, Q ₁₂ of the differential pair Cπ Decrease. Thus, the power supply voltage Vcc
Can be prevented from increasing when the total capacitance Cp decreases.

According to the frequency generation circuit 300 shown in FIG. 5, since the current adjusting circuit 51 has the function of a low-pass filter, the fluctuation of the oscillation frequency due to the low frequency fluctuation of the power supply voltage V _CC can be suppressed. It is possible to prevent high frequency noise from being mixed into the oscillation signal V ₀ when high frequency noise is mixed into the power supply voltage V _CC . At this time, as shown in the equation, since the numerator of the equation includes a term of h _fe , the capacitor C and the resistance elements R ₁ and R _{2 of the} current adjustment circuit 51 are provided.
There is an advantage that the cutoff frequency of this low-pass filter can be reduced with a small element constant of the low-pass filter.

The current adjusting circuit 51 may be configured such that the pnp transistor is an npn transistor and the npn transistor is a pnp transistor. The current sources I ₀ , IQ ₁ , IQ ₂ , IP ₁ ,
I _P2 and I ₁₀ may be constituted by resistance elements. The voltage source E ₂ constituted by the variable voltage source may supply a constant voltage from the variable voltage source. In the current adjustment circuit according to the present invention, since the element constants of the capacitor C and the resistance elements R ₁ and R ₂ are small, the cutoff frequency of the low-pass filter can be reduced, and noise can be reduced. By using this current adjustment circuit or the frequency generation circuit of the present invention including the current adjustment circuit in a tuner of a television or a radio, the size and performance of the tuner can be reduced. The above embodiment is an example of the present invention, and the present invention is not limited to the above embodiment.

[0053]

According to the present invention, when the power supply voltage fluctuates at a low frequency, it is possible to output a current following the fluctuation at the low frequency. In this case, it is possible to provide a current adjustment circuit that can prevent the output of the current following the change in the high frequency. Further, the current adjustment circuit can be configured with a small value of the capacitance of the capacitor and the resistance value of the resistance element, and a current adjustment circuit suitable for an IC can be provided.

According to the present invention, it is possible to suppress the fluctuation of the oscillation frequency due to the fluctuation of the power supply voltage at a low frequency, and to suppress the mixing of the high frequency noise in the oscillation signal when the high frequency noise is mixed in the power supply voltage. And a frequency generation circuit capable of performing the above. Further, the current adjustment circuit can be configured with a small value of the capacitance of the capacitor and the resistance value of the resistance element, and a frequency generation circuit suitable for an IC can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating an example of an oscillation circuit having a differential pair of transistors.

FIG. 2 is a circuit diagram of a frequency generation circuit including an oscillation circuit and a current adjustment circuit.

FIG. 3 is a frequency characteristic diagram of an output signal of the frequency generation circuit of FIG. 2;

FIG. 4 is a circuit diagram showing an example of a current adjustment circuit according to the present invention.

FIG. 5 is a circuit diagram showing an example of a frequency generation circuit according to the present invention.

[Explanation of symbols]

50, 51: current adjustment circuit, 55: output circuit, 100,
220: oscillation circuit, 110, 210, 310: semiconductor integrated circuit (IC), 120: external part, 200, 300
... frequency generation circuit, C ... capacitors, GND ... ground potential (earth _{potential), P 1, P 2 ...} pnp type transistor,
_{Q 1 ~Q 7, Q 11,} Q 12, Q 17 ... npn -type transistors, R _1, R ₂ ... resistance element, r ₁ ... resistance value of the resistance element R _1, r ₂ ... resistance value of the resistance element R _2, T ₀ , T ₁ ... output terminal, T _C0 ... output terminal of current adjustment circuit, T _V ... power supply voltage V
cc supply terminal, T _V0 ... input terminal of current adjustment circuit, Vcc ...
Power-supply voltage.

Claims (8)

[Claims] An emitter is connected via a resistance element, a voltage proportional to a power supply voltage is supplied to a base of one transistor, a constant voltage is supplied to a base of the other transistor, and both emitters are connected. A transistor of a first differential pair, each of which is grounded via a current source; a first transistor having an emitter connected to a collector of the one transistor and a collector connected to a supply terminal of the power supply voltage; A second transistor having an emitter connected to the collector of the other transistor and having a collector connected to the power supply voltage supply terminal; one end connected to a base of the first transistor; a base of the second transistor; A capacitor having the other end connected to the other end thereof; a base of one transistor connected to the one end of the capacitor; Is connected to the base of the other transistor, the emitters are connected to each other via a resistance element,
A second differential pair of transistors, both emitters of which are connected to a supply terminal of the power supply voltage via a current source, respectively, and a second differential pair of transistors connected to both collectors of the second differential pair of transistors. A current adjustment circuit comprising: a current mirror circuit that controls a collector current; and an output circuit that outputs a current according to the collector current. 2. An output circuit comprising: a diode having an anode connected to a collector of the one of the transistors of the second differential pair, and a cathode having a cathode grounded through a resistor element; A constant current source for outputting a current, a third transistor having a base connected to the anode, an emitter grounded via a resistance element, and an output terminal connected to a collector of the third transistor. Item 2. The current adjustment circuit according to Item 1. 3. The current adjustment circuit according to claim 1, wherein a constant voltage is supplied to each base of the transistors of the second differential pair via respective resistance elements to supply a bias voltage. 4. The current adjustment circuit according to claim 1, wherein said first, second and third transistors are each an npn-type transistor, and said first and second transistors have the same characteristics. 5. A power supply voltage supply terminal, a collector of one transistor is connected via a resistance element, a power supply voltage supply terminal is connected to a collector of the other transistor, and a connection point between emitters serves as a current source. Grounded through,
A constant voltage is supplied to each base via a resistance element, and a bias voltage is supplied to the differential pair of transistors. One end of the transistor of the differential pair is connected to a collector of the one transistor. A first capacitor, a second capacitor having one end connected to the base of the other transistor of the differential pair of transistors, and the other end connected to the other end of the first capacitor; An oscillation circuit having a resonance circuit connected to the other end of the capacitor, and emitters connected to each other via a resistance element, and a voltage proportional to the power supply voltage is supplied to a base of one of the transistors, and A first differential pair of transistors having a constant voltage supplied to a base of the transistor, and both emitters grounded via a current source; A first transistor having an emitter connected to the collector of the one of the transistors of the moving pair and having a collector connected to the supply terminal of the power supply voltage; and the other of the transistors of the first differential pair A second transistor having an emitter connected to the collector of the transistor, and a collector connected to the supply terminal of the power supply voltage; one end connected to the base of the first transistor; and the other end connected to the base of the second transistor. Connected to a capacitor, the one end of the capacitor is connected to the base of one transistor, the other end is connected to the base of the other transistor, the emitters are connected via a resistance element,
A second differential pair of transistors, both emitters of which are connected to a supply terminal of the power supply voltage via a current source; A current mirror circuit for controlling a collector current; and an output circuit for outputting a current corresponding to the collector current to a connection point between the emitters of the oscillation circuit. A frequency generating circuit, wherein an output terminal for outputting an oscillation signal is connected to the one end or the one end of the second capacitor. 6. The output circuit, comprising: a diode having an anode connected to a collector of the one of the transistors of the second differential pair and a cathode grounded via a resistance element; A constant current source that outputs a current; a third transistor having a base connected to the anode, an emitter grounded via a resistor, and a collector connected to a connection point between the emitters of the oscillation circuit. The frequency generation circuit according to claim 5. 7. The frequency generation circuit according to claim 5, wherein a constant voltage is supplied to each base of the transistors of the second differential pair via respective resistance elements, and a bias voltage is supplied. 8. The frequency generating circuit according to claim 5, wherein said first, second and third transistors are each an npn-type transistor, and said first and second transistors have the same characteristics.