CN103905037B - A kind of host-guest architecture frequency calibration circuit for Gm-C wave filter - Google Patents

Abstract

The invention discloses a master-slave structure frequency calibration circuit for a Gm-C filter, the frequency calibration circuit includes a transconductance amplifier master-slave structure control circuit, an RC oscillator circuit and a digital logic circuit; the master-slave structure control circuit The master transconductance amplifier matches the slave transconductance amplifier in the Gm-C filter, and is controlled by the same bias voltage, so that its transconductance value Gm is precisely inversely proportional to the resistance R in the master-slave control circuit, and the transconductance amplifier The effect of process error on frequency is transformed into the effect of resistance process error on frequency. Compared with the traditional Gm-C filter, the frequency calibration circuit has the characteristics of simple structure and good robustness.

Description

A master-slave structure frequency calibration circuit for Gm-C filter

technical field

The invention relates to a master-slave structure frequency calibration circuit for Gm-C filter.

Background technique

The calibration circuit is an essential module in the integrated filter circuit. With the development of semiconductor integrated circuits, analog and digital single chips are becoming more and more mainstream. Low-IF filters, as key circuits for radio frequency transceivers and sensor interfaces, are often selected to be integrated on chips to reduce system size and cost. and improve system performance. However, due to process factors such as manufacturing tolerances, process changes, and device aging, the frequency characteristics of the filter will change greatly. For example, a process deviation of 20% in resistors and capacitors will cause a 30% to 50% error in filter frequency. The solution is to add a frequency calibration circuit in the integrated filter, and adjust the parameters of the device adaptively, so that the frequency characteristics of the filter can achieve the required functions.

Different types of integrated filters have different frequency calibration circuits. The frequency characteristics of the active RC filter are determined by the RC time constant. The resistors and capacitors are in the form of an array, and the frequency characteristics of the filter can be changed by changing the code rate of the array through digital logic. The frequency detection circuit can be realized by an integrator or an oscillator. . The detection circuit based on the integrator requires high power consumption and complex structure due to the processing of analog signals such as amplifiers and comparators, while the detection circuit based on the oscillator can be realized with only an inverter, low power consumption and simple structure, so in low Power consumption applications often use oscillator-based frequency calibration circuits. Different from active RC filters, Gm-C filters have the characteristics of ultra-low power consumption, so Gm-C filters are often used in mainstream low-power design circuits. However, the frequency characteristic of the Gm-C filter is determined by the time constant C/Gm, where Gm is the transconductance value of the operational transconductance amplifier, which is determined by the tail current source. It is generally changed by adjusting the bias voltage, and only continuous analog signal conditioning. The traditional PLL-based Gm-C filter frequency calibration circuit mainly includes three modules: a voltage-controlled oscillator, a phase detector, and a low-pass filter, as shown in Figure 2. The oscillator, phase detector and low-pass filter form a control loop. After the loop is locked, the oscillation frequency of the voltage-controlled oscillator VCO is the same as the input reference clock frequency of the phase detector. The voltage-controlled oscillator VCO and the Gm-C filter The transconductance amplifier and capacitance in the detector are matched, so the frequency characteristics in the Gm-C filter can be determined by determining the input reference frequency of the phase detector. However, several modules of this calibration circuit need to consume a lot of power consumption, and at the same time, the voltage-controlled oscillator still has problems of limiting and stability.

The master-slave control idea of the transconductance amplifier first appeared in the variable gain amplifier. To achieve high-precision gain adjustment, the variable gain amplifier requires high accuracy of the transconductance value of the transconductance amplifier. The transconductance of the transconductance amplifier The value is usually related to multiple device parameters, and it is also a simple linear correlation, so direct regulation is difficult to achieve high accuracy. The master-slave structure is adopted, and the transconductance value is converted into a variable linearly related to a certain parameter through the master transconductance amplifier, such as voltage value or clock frequency. The reference voltage or reference clock provided by the system can convert the transconductance amplifier’s The transconductance value is fixed at an accurate value, and the slave transconductance amplifier in the variable gain amplifier is controlled by the master transconductance amplifier, thereby realizing a high-precision gain value.

Therefore, a new master-slave frequency calibration circuit for Gm-C filters is needed to solve the above problems.

Contents of the invention

Purpose of the invention: The present invention aims at the defects of variable gain amplifiers in the prior art, and provides a master-slave structure frequency calibration circuit for Gm-C filters that increases the range of gain variation.

Technical solution: In order to solve the above technical problems, the master-slave structure frequency calibration circuit for Gm-C filter of the present invention adopts the following technical solution:

A master-slave structure frequency calibration circuit for Gm-C filter, including transconductance amplifier master-slave control circuit,

The transconductance amplifier master-slave control circuit includes a first P-type metal oxide field effect transistor (PM1), a second P-type metal oxide field effect transistor (PM2), a third P-type metal oxide field effect transistor (PM3 ), the fourth P-type MOSFET (PM4), the fifth P-type MOSFET (PM5), the sixth P-type MOSFET (PM6), the seventh P-type MOSFET Object field effect transistor (PM7), eighth P-type metal oxide field effect transistor (PM8), ninth P-type metal oxide field effect transistor (PM9), tenth P-type metal oxide field effect transistor (PM10), The eleventh P-type MOSFET (PM11), the twelfth P-type MOSFET (PM12), the first N-type MOSFET (NM1), the second N-type MOSFET Object FET (NM2), third N-type MOSFET (NM3), fourth N-type MOSFET (NM4), fifth N-type MOSFET (NM5), A sixth NMOSFET (NM6) and a resistor (R0) and a main transconductance amplifier (Gm),

The source of the first P-type metal oxide field effect transistor (PM1), the source electrode of the second P-type metal oxide field effect transistor (PM2), the third P-type metal oxide field effect transistor (PM3), the source of the fourth PMOSFET (PM4), the source of the fifth PMOSFET (PM5), and the sixth PMOSFET The source of the type metal oxide field effect transistor (PM6) is connected and connected to the power supply;

The gate of the first P-type metal oxide field effect transistor (PM1), the gate of the second P-type metal oxide field effect transistor (PM2), the third P-type metal oxide field effect transistor (PM3), the gate of the fourth PMOSFET (PM4), the gate of the fifth PMOSFET (PM5), and the sixth PMOSFET The gate connection of the metal oxide field effect transistor (PM6);

The drain of the first P-type metal oxide field effect transistor (PM1), the source of the seventh P-type metal oxide field effect transistor (PM7), and the eighth P-type metal oxide field effect transistor (PM8) source connection;

The drain of the second P-type MOSFET (PM2) is connected to the source of the ninth P-type MOSFET (PM9);

The drain of the third P-type MOSFET (PM3) is connected to the non-inverting input terminal and the inverting output terminal of the main transconductance amplifier (Gm);

The drain of the fourth P-type MOSFET (PM4) is connected to the source of the tenth P-type MOSFET (PM10);

The drain of the fifth P-type MOSFET (PM5) is connected to the source of the eleventh P-type MOSFET (PM11);

The drain of the sixth P-type metal oxide field effect transistor (PM6), the gate of the sixth P-type metal oxide field effect transistor (PM6), and the twelfth P-type metal oxide field effect transistor (PM6) The source connection of the tube (PM12);

The drain of the seventh P-type metal oxide field effect transistor (PM7), the drain of the first N-type metal oxide field effect transistor (NM1), the first N-type metal oxide field effect transistor The gate of (NM1) is connected to the gate of the second NMOSFET (NM2);

The gate of the seventh P-type metal oxide field effect transistor (PM7) is connected to the non-inverting input terminal and the inverting output terminal of the main transconductance amplifier (Gm);

The drain of the eighth P-type MOSFET (PM8) is connected to the drain of the second N-type MOSFET (NM2);

connecting the gate of the eighth PMOSFET (PM8), the drain of the tenth PMOSFET (PM10) and one end of a resistor (R0);

The gate of the ninth P-type metal oxide field effect transistor (PM9), the gate of the tenth P-type metal oxide field effect transistor (PM10), the eleventh P-type metal oxide field effect transistor The gate of the transistor (PM11) is connected to the gate of the twelfth P-type metal oxide field effect transistor (PM12);

The drain of the ninth P-type metal oxide field effect transistor (PM9), the drain of the third N-type metal oxide field effect transistor (NM3), the third N-type metal oxide field effect transistor The gate of (NM3) is connected to the gate of the fourth NMOSFET (NM4);

The drain of the tenth P-type metal oxide field effect transistor (PM10) is connected to the drain of the fifth P-type metal oxide field effect transistor (PM5) and the fourth P-type metal oxide field effect transistor (PM5) through the resistor (R0). The drain of the oxide field effect transistor (PM4);

The drain of the eleventh P-type metal oxide field effect transistor (PM11), the gate of the sixth N-type metal oxide field effect transistor (NM6), the sixth N-type metal oxide field effect transistor The drain of the transistor (NM6) is connected to the gate of the fifth NMOSFET (NM5);

The drain of the twelfth P-type metal oxide field effect transistor (PM12) is connected to the input end of the reference current source (Iref);

The drain of the fourth NMOSFET (NM4), the drain of the fifth NMOSFET (NM5), and the inverting phase of the main transconductance amplifier (Gm) The input terminal is connected to the non-inverting output terminal of the main transconductance amplifier (Gm);

The source of the first NMOSFET (NM1), the source of the second NMOSFET (NM2), the third NMOSFET (NM3), the source of the fourth NMOSFET (NM4), the fifth NMOSFET (NM5), the sixth NMOSFET The source of the MOSFET (NM6) and the output of the reference current source (Iref) are grounded;

The drain of the second NMOSFET (NM2) is connected to the voltage control port of the master transconductance amplifier (Gm) and the voltage control port of the slave transconductance amplifier in the Gm-C filter.

Further, it also includes an RC oscillator circuit, the RC oscillator circuit includes a first inverting amplifier (Inv0), a second inverting amplifier (Inv1), a third inverting amplifier (Inv2), a variable capacitor (C0), The first resistor (R1) and the second resistor (R2), the first inverting amplifier (Inv0), the second inverting amplifier (Inv1) and the third inverting amplifier (Inv2) are connected end to end in sequence, and the first The first resistor (R1) and the second resistor (R2) are set between an inverting amplifier (Inv0) and a third inverting amplifier (Inv2), and the first resistor (R1) and the second resistor (R2 ) are connected in series; one end of the variable capacitor (C0) is connected to the connection point of the second inverting amplifier (Inv1) and the third inverting amplifier (Inv2), and the other end of the variable capacitor (C0) is connected to The connection point of the first resistor (R1) and the second resistor (R2). A low-power RC frequency detection circuit is used to calibrate the time constant of the filter by adjusting the capacitance value. Compared with the voltage-controlled oscillator VCO, the RC oscillator circuit has no input limit and stability problems, and has low power consumption. This calibration circuit is very suitable for low-power, low-cost Gm-C filters. It can effectively save power consumption and save circuit structure.

Further, it also includes a digital logic circuit, the RC oscillating circuit is connected to the digital logic circuit, and the transconductance amplifier master-slave control circuit and the digital logic circuit are respectively connected to the slave transconductance amplifier in the Gm-C filter. voltage control port and capacitance control port,

The digital logic circuit is used to detect the frequency of the RC oscillating circuit and adjust the adjustable capacitance value to stabilize the oscillation frequency within a fixed range, correct the time constant RC, and finally send the calibrated capacitance value to the Gm-C filter.

Beneficial effects: the circuit structure of the master-slave frequency calibration circuit for the Gm-C filter of the present invention is simple, and a frequency calibration circuit for the Gm-C filter is provided. The frequency error of the Gm-C filter is mainly affected by the transconductance value of the transconductance amplifier and the process error and temperature of the capacitor. There are many factors affecting the transconductance value Gm of the transconductance amplifier, so a circuit that accurately controls the transconductance value is required . The calibration circuit uses the master-slave control structure of the transconductance amplifier, which converts the error of the transconductance amplifier into the process deviation of the resistance, and has higher stability.

Description of drawings

Fig. 1 is the master-slave structure frequency calibration circuit frequency calibration circuit module block diagram for Gm-C filter of the present invention;

Fig. 2 is a block diagram of a traditional Gm-C filter frequency calibration circuit based on a phase-locked loop;

Fig. 3 is key module transconductance amplifier master-slave control circuit schematic diagram among the present invention;

Fig. 4 is the comparison of the amplitude-frequency characteristic curves before and after calibration of the Gm-C low-pass filter under different process angles after adopting the frequency calibration circuit of the present invention: M0 is an ideal curve, M1 and M2 are before calibration under FF and SS process angles respectively The curves of M3 and M4 are the calibrated curves under the FF and SS process corners.

detailed description

Below in conjunction with accompanying drawing and specific embodiment the present invention is described in further detail:

Please refer to shown in Fig. 1, the master-slave structure frequency calibration circuit for the Gm-C filter of the present invention comprises transconductance amplifier master-slave control circuit,

The transconductance amplifier master-slave control circuit includes a first P-type MOSFET PM1, a second P-type MOSFET PM2, a third P-type MOSFET PM3, and a fourth P-type MOSFET. The object field effect transistor PM4, the fifth P-type metal oxide field effect transistor PM5, the sixth P-type metal oxide field effect transistor PM6, the seventh P-type metal oxide field effect transistor PM7, the eighth P-type metal oxide field effect transistor Effect tube PM8, ninth P-type MOSFET PM9, tenth P-type MOSFET PM10, eleventh P-type MOSFET PM11, twelfth P-type MOSFET Effect tube PM12, first N-type MOSFET NM1, second N-type MOSFET NM2, third N-type MOSFET NM3, fourth N-type MOSFET NM4, the fifth NMOSFET NM5, the sixth NMOSFET NM6, the resistor R0 and the main transconductance amplifier Gm.

Among them, the source of the first P-type MOSFET PM1, the source of the second P-type MOSFET PM2, the source of the third P-type MOSFET PM3, the fourth PMOSFET The source of the P-type Mosfet PM4, the source of the fifth P-type Mosfet PM5 and the source of the sixth P-type Mosfet PM6 are connected and connected to the power supply. The gate of the first P-type metal oxide field effect transistor PM1, the gate of the second P-type metal oxide field effect transistor PM2, the gate of the third P-type metal oxide field effect transistor PM3, the fourth P-type metal oxide field effect transistor The gate of the MOSFET PM4, the gate of the fifth PMOSFET PM5 and the gate of the sixth PMOSFET PM6 are connected. The drain of the first PMOSFET PM1, the source of the seventh PMOSFET PM7 and the source of the eighth PMOSFET PM8 are connected. The drain of the second PMOSFET PM2 is connected to the source of the ninth PMOSFET PM9. The drain of the third PMOSFET PM3 is connected to the non-inverting input terminal and the inverting output terminal of the main transconductance amplifier Gm. The drain of the fourth PMOSFET PM4 is connected to the source of the tenth PMOSFET PM10 . The drain of the fifth PMOSFET PM5 is connected to the source of the eleventh PMOSFET PM11. The drain of the sixth PMOSFET PM6, the gate of the sixth PMOSFET PM6 and the source of the twelfth PMOSFET PM12 are connected. The drain of the seventh PMOSFET PM7, the drain of the first NMOSFET NM1, the gate of the first NMOSFET NM1 and the second NMOSFET Gate connection of oxide field effect transistor NM2. The gate of the seventh PMOSFET PM7 is connected to the non-inverting input terminal and the inverting output terminal of the transconductance amplifier Gm. The drain of the eighth PMOSFET PM8 is connected to the drain of the second NMOSFET NM2 . The gate of the eighth PMOSFET PM8, the drain of the tenth PMOSFET PM10 are connected to one end of the resistor R0. The gate of the ninth P-type metal oxide field effect transistor PM9, the gate of the tenth P-type metal oxide field effect transistor PM10, the gate of the eleventh P-type metal oxide field effect transistor PM11, and the grid of the twelfth P-type metal oxide field effect transistor Type metal oxide field effect transistor PM12 gate connection. The drain of the ninth P-type metal oxide field effect transistor PM9, the drain of the third N-type metal oxide field effect transistor NM3, the gate of the third N-type metal oxide field effect transistor NM3, the fourth N-type metal oxide field effect transistor Gate connection of oxide field effect transistor NM4. The drain of the tenth PMOSFET PM10 is connected to the drain of the fifth PMOSFET PM5 and the drain of the fourth PMOSFET PM4 through the resistor R0 . The drain of the eleventh P-type metal oxide field effect transistor PM11, the gate of the sixth N-type metal oxide field effect transistor NM6, the drain of the sixth N-type metal oxide field effect transistor NM6 and the fifth N-type metal oxide field effect transistor Gate connection of Mosfet NM5. The drain of the twelfth PMOSFET PM12 is connected to the input terminal of the reference current source Iref. The drain of the fourth N-type metal oxide field effect transistor NM4, the drain of the fifth N-type metal oxide field effect transistor NM5, the inverting input terminal of the main transconductance amplifier Gm, and the non-inverting output terminal of the main transconductance amplifier Gm connect.

The source of the first NMOSFET NM1, the source of the second NMOSFET NM2, the source of the third NMOSFET NM3, the fourth NMOSFET The source of the MOSFET NM4 , the source of the fifth NMOSFET NM5 , the source of the sixth NMOSFET NM6 and the output terminal of the reference current source Iref are all grounded. The drain of the second NMOSFET NM2 is connected to the voltage control port of the master transconductance amplifier Gm and the voltage control port of the slave transconductance amplifier in the Gm-C filter.

Also includes an RC oscillating circuit, the RC oscillating circuit includes a first inverting amplifier Inv0, a second inverting amplifier Inv1, a third inverting amplifier Inv2, a variable capacitor C0, a first resistor R1 and a second resistor R2, the first inverting The amplifier Inv0, the second inverting amplifier Inv1 and the third inverting amplifier Inv2 are sequentially connected end to end, the first resistor R1 and the second resistor R2 are arranged between the first inverting amplifier Inv0 and the third inverting amplifier Inv2, the first The resistor R1 and the second resistor R2 are connected in series. One end of the variable capacitor C0 is connected to the connection point of the second inverting amplifier Inv1 and the third inverting amplifier Inv2, and the other end of the variable capacitor C0 is connected to the connection point of the first resistor R1 and the second resistor R2. A low-power RC frequency detection circuit is used to calibrate the time constant of the filter by adjusting the capacitance value. Compared with the voltage-controlled oscillator VCO, the RC oscillator circuit has no input limit and stability problems, and has low power consumption. This calibration circuit is very suitable for low-power, low-cost Gm-C filters. It can effectively save power consumption and save circuit structure.

It also includes a digital logic circuit, the RC oscillator circuit is connected to the digital logic circuit, the transconductance amplifier master-slave control circuit and the digital logic circuit are respectively connected to the voltage control port and the capacitance control port of the slave transconductance amplifier in the Gm-C filter, and the digital logic circuit is used It is used to detect the frequency of the RC oscillator circuit and adjust the adjustable capacitance value to stabilize the oscillation frequency within a fixed range, correct the time constant RC, and finally send the calibrated capacitance value to the Gm-C filter. The digital logic circuit is a common functional module in the prior art, which is not improved in the present invention.

Invention principle:

The core of the calibration circuit of the present invention is the transconductance amplifier master-slave control circuit as shown in Figure 3, including the master transconductance amplifier, current source _ib , ig, resistance R0 and error amplifier: in order to ensure that the input and output common mode levels are equal, the master The transconductance amplifier is connected in the form of negative feedback; the current source i _b flows through the resistor R0 to generate a fixed voltage difference V′ _p -V _n =i _b R, the inverting input of the transconductance amplifier is connected to the resistor and the voltage at one end is fixed at Vn, and the non-inverting input The terminal and the other end of the resistor are respectively connected to the input of the error amplifier, so that the input voltage of the transconductance amplifier is equal to the voltage difference i _b R between the two ends of the resistor. The current source ig sinks/sinks current ig from the output of the transconductance amplifier. Since the input voltage and output current of the transconductance amplifier are fixed, its transconductance value is The current source is obtained from the reference image, and its error is very small. The transconductance value of the transconductance amplifier is inversely proportional to the resistance R, and its precision is also determined by the resistance.

The master-slave structure controls the transconductance amplifier in the Gm-C filter, so that its transconductance value Gm is precisely inversely proportional to the resistance R in the master-slave control circuit (G _m = k ₁ /R, k ₁ is a constant), so The time constant that determines the frequency characteristics of the Gm-C filter (including bandwidth, center frequency, etc.) f changes from C/Gm to RC, expressed as f∝G _m /C=k ₁ /RC. The oscillation frequency f ₀ of the RC oscillator circuit is inversely proportional to the time constant RC (f ₀ =k ₂ /RC), where the resistance R and capacitance C match the resistance in the master-slave control circuit and the capacitance in the Gm-C filter respectively, Therefore, the frequency characteristic of the Gm-C filter is proportional to the oscillation frequency of the RC oscillator, ie f∝f ₀ =k ₂ /RC. The digital logic circuit detects the frequency of the oscillating circuit and adjusts the adjustable capacitor value to stabilize the oscillating frequency within a fixed range, realize the correction of the time constant RC, and finally send the calibrated capacitor value to the Gm-C filter, and finally realize the Gm - Frequency calibration of the C filter.

Compared with the traditional phase-locked loop-based Gm-C filter frequency calibration circuit shown in Figure 2, except for the master-slave control circuit that consumes a certain amount of quiescent current, the other modules of the calibration circuit are all digital circuits and can only be activated after calibration. Closed, has the characteristics of low power consumption. Compared with the voltage-controlled oscillator VCO, the RC oscillator circuit has no input limit and stability problems, and at the same time has low power consumption. This calibration circuit is very suitable for low-power, low-cost Gm -C filter.

As shown in FIG. 4 , the amplitude-frequency characteristic curves of the Gm-C low-pass filter before and after calibration at different process angles after using the frequency calibration circuit of the present invention. Among them, M0 is the ideal amplitude-frequency characteristic curve with a bandwidth of 244KHz; M1 and M2 are the amplitude-frequency characteristics under the FF and SS process angles before calibration, respectively, and the bandwidths are 335KHz and 174KHz respectively, and the frequency error is nearly 30%; M3 and M4 are respectively The calibrated amplitude-frequency characteristics under the FF and SS process corners have bandwidths of 250KHz and 237KHz respectively, and the frequency error is reduced to within 5%. It can be seen that the calibration circuit of the present invention realizes the frequency calibration function.

Based on the master-slave control idea of the transconductance amplifier, the present invention combines the frequency calibration circuit of the active RC filter, and proposes a new master-slave structure frequency calibration circuit frequency calibration circuit for the Gm-C filter, the circuit structure Simple, low power consumption, and good stability, it really meets the characteristics of low power consumption and low cost of the Gm-C filter.

Compared with the traditional Gm-C filter frequency calibration circuit based on phase-locked loop, except the master-slave control circuit consumes a certain quiescent current, the other modules of the calibration circuit are all digital circuits and can be closed only after the calibration is completed. The characteristics of low power consumption, compared with the voltage-controlled oscillator VCO, the RC oscillator circuit has no input limit and stability problems, and at the same time has low power consumption. This calibration circuit is very suitable for low-power, low-cost Gm-C filtering device.

Wherein, the calibration circuit includes a transconductance amplifier master-slave control circuit, an RC oscillator circuit and a digital logic circuit, the master transconductance amplifier in the transconductance amplifier master-slave control circuit matches the slave transconductance amplifier in the Gm-C filter, Controlled by the same bias voltage; the master-slave control circuit converts the transconductance value Gm of the transconductance amplifier into an inversely proportional relationship with the resistance R in the control circuit, and the resistance R in the RC oscillator circuit is inversely proportional to the resistance R in the master-slave structure transconductance amplifier The resistor R matches, and the adjustable capacitor C matches the adjustable capacitor C in the Gm-C filter; the digital logic circuit detects the oscillation frequency of the RC oscillator and adjusts the adjustable capacitor C to stabilize the oscillation frequency within a fixed range, and Send the stable value of the adjustable capacitor to the Gm-C filter. In this calibration circuit, a master-slave structure is used to control the transconductance amplifier in the Gm-C filter, so that the transconductance value Gm is precisely inversely proportional to the resistance R in the master-slave control circuit, and the process error of the transconductance amplifier is transformed into resistance R The process error, so that the time constant that determines the frequency characteristics of the Gm-C filter is changed from C/Gm to the same RC as the active RC filter. The resistor R and capacitor C in the RC oscillating circuit are respectively matched with the resistors in the master-slave control circuit and the capacitor in the Gm-C filter, so as to accurately reflect the frequency characteristics of the filter. The digital logic circuit detects the output frequency of the oscillating circuit and adjusts the adjustable capacitance value, and finally sends the calibrated capacitance value to the Gm-C filter, thereby realizing the frequency calibration of the Gm-C filter. Compared with the traditional Gm-C filter, the frequency calibration circuit has the characteristics of simple structure, low power consumption and good robustness.

The master-slave structure frequency calibration circuit for Gm-C filter of the present invention provides a frequency calibration circuit for Gm-C filter. The frequency error of the Gm-C filter is mainly affected by the transconductance value of the transconductance amplifier and the process error and temperature of the capacitor. There are many factors affecting the transconductance value Gm of the transconductance amplifier, so a circuit that accurately controls the transconductance value is required . The calibration circuit uses the master-slave control structure of the transconductance amplifier, which converts the error of the transconductance amplifier into the process deviation of the resistance, and has higher stability.

Claims (3)

1. a kind of master-slave structure frequency calibration circuit for Gm-C filter, it is characterized in that, comprise transconductance amplifier master-slave control circuit, described transconductance amplifier master-slave control circuit comprises the first P-type metal oxide field Effect transistor (PM1), second P-type MOSFET (PM2), third P-type MOSFET (PM3), fourth P-type MOSFET (PM4), fifth P-type MOSFET (PM5), sixth P-type MOSFET (PM6), seventh P-type MOSFET (PM7), eighth P-type MOSFET (PM8), the ninth P-type MOSFET (PM9), the tenth P-type MOSFET (PM10), the eleventh P-type MOSFET (PM11), the twelfth P-type MOSFET (PM12), first N-type MOSFET (NM1), second N-type MOSFET (NM2), third N-type MOSFET (NM3), the fourth NMOSFET (NM4), the fifth NMOSFET (NM5), the sixth NMOSFET (NM6) and the resistor (R0) and main transconductance amplifier (Gm); The source of the first P-type metal oxide field effect transistor (PM1), the source electrode of the second P-type metal oxide field effect transistor (PM2), and the third P-type metal oxide field effect transistor (PM3), the source of the fourth P-type MOSFET (PM4), the source of the fifth P-type MOSFET (PM5), and the sixth PMOS The source of the metal oxide field effect transistor (PM6) is connected and connected to the power supply; The gate of the first P-type metal oxide field effect transistor (PM1), the gate gate of the second P-type metal oxide field effect transistor (PM2), the third P-type metal oxide field effect transistor (PM3), the grid of the fourth PMOSFET (PM4), the grid of the fifth PMOSFET (PM5), and the sixth PMOSFET The gate connection of the metal oxide field effect transistor (PM6); The drain of the first P-type metal oxide field effect transistor (PM1), the source of the seventh P-type metal oxide field effect transistor (PM7), and the eighth P-type metal oxide field effect transistor (PM8) source connection; The drain of the second P-type MOSFET (PM2) is connected to the source of the ninth P-type MOSFET (PM9); The drain of the third P-type metal oxide field effect transistor (PM3) is connected to the non-inverting input terminal and the inverting output terminal of the main transconductance amplifier (Gm); The drain of the fourth P-type MOSFET (PM4) is connected to the source of the tenth P-type MOSFET (PM10); The drain of the fifth P-type MOSFET (PM5) is connected to the source of the eleventh P-type MOSFET (PM11); The drain of the sixth P-type metal oxide field effect transistor (PM6), the gate of the sixth P-type metal oxide field effect transistor (PM6), and the twelfth P-type metal oxide field effect transistor The source connection of the tube (PM12); The drain of the seventh P-type metal oxide field effect transistor (PM7), the drain electrode of the first N-type metal oxide field effect transistor (NM1), the first N-type metal oxide field effect transistor The gate of (NM1) is connected to the gate of the second NMOSFET (NM2); The gate of the seventh P-type metal oxide field effect transistor (PM7) of the non-inverting input terminal is connected to the non-inverting input terminal and the inverting output terminal of the transconductance amplifier (Gm); The drain of the eighth P-type MOSFET (PM8) is connected to the drain of the second N-type MOSFET (NM2); A connection between the gate of the eighth PMOSFET (PM8), the drain of the tenth PMOSFET (PM10) and one end of the resistor (R0); The gate of the ninth P-type metal oxide field effect transistor (PM9), the gate of the tenth P-type metal oxide field effect transistor (PM10), the eleventh P-type metal oxide field effect transistor The grid of the tube (PM11) is connected to the grid of the twelfth P-type metal oxide field effect transistor (PM12); The drain of the ninth P-type metal oxide field effect transistor (PM9), the drain electrode of the third N-type metal oxide field effect transistor (NM3), the third N-type metal oxide field effect transistor The gate of (NM3) is connected to the gate of the fourth NMOSFET (NM4); The drain of the tenth P-type metal oxide field effect transistor (PM10) is connected to the drain of the fifth P-type metal oxide field effect transistor (PM5) and the fourth P-type metal oxide field effect transistor (PM5) through the resistor (R0). The drain of the oxide field effect transistor (PM4); The drain of the eleventh P-type metal oxide field effect transistor (PM11), the gate of the sixth N-type metal oxide field effect transistor (NM6), the sixth N-type metal oxide field effect transistor The drain of the tube (NM6) is connected to the gate of the fifth NMOSFET (NM5); The drain of the twelfth P-type MOSFET (PM12) is connected to the input terminal of the reference current source (Iref); The drain of the fourth NMOSFET (NM4), the drain of the fifth NMOSFET (NM5), and the inverting phase of the main transconductance amplifier (Gm) The input terminal is connected with the same phase output terminal of the main transconductance amplifier (Gm); The source of the first NMOSFET (NM1), the source of the second NMOSFET (NM2), and the third NMOSFET (NM3), the source of the fourth NMOSFET (NM4), the fifth NMOSFET (NM5), the sixth NMOSFET The source of the Type Mosfet (NM6) and the output end of the reference current source (Iref) are all grounded; The drain of the second NMOSFET (NM2) is connected to the voltage control port of the main transconductance amplifier (Gm) and the voltage control port of the slave transconductance amplifier in the Gm-C filter. 2. the master-slave structure frequency calibration circuit for Gm-C filter as claimed in claim 1, is characterized in that, also comprises RC oscillation circuit, and described RC oscillation circuit comprises the first inverting amplifier (Inv0), the first Two inverting amplifiers (Inv1), a third inverting amplifier (Inv2), a variable capacitor (C0), a first resistor (R1) and a second resistor (R2), the first inverting amplifier (Inv0), the Two inverting amplifiers (Inv1) and the third inverting amplifier (Inv2) are connected end to end in sequence, and the first resistor ( R1) and the second resistor (R2), the first resistor (R1) and the second resistor (R2) are connected in series; one end of the variable capacitor (C0) is connected to the second inverting amplifier (Inv1) and The connection point of the third inverting amplifier (Inv2), the other end of the variable capacitor (C0) is connected to the connection point of the first resistor (R1) and the second resistor (R2). 3. the master-slave structure frequency calibration circuit for Gm-C filter as claimed in claim 1, is characterized in that, also comprises RC oscillatory circuit and digital logic circuit, described RC oscillatory circuit connects described digital logic circuit, The master-slave control circuit of the transconductance amplifier and the digital logic circuit are respectively connected to the voltage control port and the capacitance control port of the transconductance amplifier in the Gm-C filter, and the digital logic circuit is used to detect the voltage of the RC oscillator circuit Frequency and adjust the adjustable capacitor value to stabilize the oscillation frequency within a fixed range, correct the time constant RC, and finally send the calibrated capacitor value to the Gm-C filter.