Variable gain amplifier

Abstract

The utility model relates to a variable gain amplifier which comprises a first VGA module, a second VGA module and a gain adjusting module, the first VGA module and the second VGA module work at the same bias voltage, and the gain adjusting module is arranged to provide a direct-current voltage (namely a differential input signal) for the second VGA module. And the gain adjusting module adjusts the bias voltage according to the deviation between the direct current voltage of the actual gain and the direct current voltage of the target gain, and maintains the actual gain of the first VGA module and the second VGA module consistent with the target gain, so that even if the actual gain is influenced by the change of the process and the temperature and the deviation with the target gain exists, the gain of the first VGA module and the second VGA module is not influenced. And the gain adjusting module can also realize a closed-loop adjusting process of gain deviation, and the problem that the gain of the variable gain amplifier cannot be kept stable due to reasons such as process deviation and temperature change is solved.

Description

Technical Field

[0001] The present application belongs to the field of electronic circuit technology, and in particular to a variable gain amplifier. Background Art

[0002] In normal working state, the gain of variable gain amplifier (VGA) can be adjusted. After adjusting to the required state, the gain of VGA is fixed. However, in actual application, due to process deviation and temperature change, the same VGA gain control bias voltage will cause the actual gain of VGA to vary greatly and cannot maintain stability, which will affect the performance of the entire circuit system. Utility Model Content

[0003] The purpose of the present application is to provide a variable gain amplifier, aiming to solve the problem that the gain of a conventional variable gain amplifier cannot be maintained stable due to process deviations and temperature changes.

[0004] The embodiment of the present application provides a variable gain amplifier, including a first VGA module, a second VGA module and a gain adjustment module;

[0005] The bias voltage terminal of the second VGA module is connected to the bias voltage terminal of the first VGA module and is connected to a bias voltage for configuring gain. The input terminal of the second VGA module is used to connect a differential input terminal signal. The second VGA module is used to perform actual gain on the voltage difference of the differential input terminal signal based on the bias voltage and then output it.

[0006] The input end of the gain adjustment module is connected to the output end of the second VGA module, and the output end of the gain adjustment module is connected to the bias voltage end. The gain adjustment module is used to adjust the bias voltage according to the deviation between the voltage difference after actual gain and the voltage difference of target gain, so as to maintain the actual gain of the first VGA module consistent with the target gain.

[0007] In some embodiments, the gain adjustment module is specifically used to:

[0008] When the voltage difference after the actual gain is greater than the voltage difference of the target gain, outputting a first regulating voltage, wherein the first regulating voltage is used to adjust the bias voltage to reduce the actual gain;

[0009] In the case where the voltage difference after actual gain is less than the voltage difference after target gain, a second regulating voltage is output to regulate the bias voltage to increase the actual gain.

[0010] In some embodiments, the low frequency gain of the first VGA module is the same as the low frequency gain of the second VGA module.

[0011] In some embodiments, the gain adjustment module includes a first amplification unit and a second amplification unit;

[0012] The first positive input terminal of the first amplifying unit is connected to the negative output terminal of the second VGA module, and the second positive input terminal of the first amplifying unit is connected to the first reference voltage; the inverting input terminal of the first amplifying unit is connected to the positive output terminal of the second VGA module;

[0013] One of the two input terminals of the second amplifying unit is connected to the output terminal of the first amplifying unit, and the other is connected to a second reference voltage, and the output terminal of the second amplifying unit is connected to the bias voltage terminal;

[0014] The second reference voltage=the voltage difference of the target gain×the gain of the first amplifying unit+the first reference voltage.

[0015] In some embodiments, the gain adjustment module further includes a voltage source, which is connected to the second amplifier. The voltage source includes a gain setting terminal for setting the target gain, and the voltage source is used to provide the voltage difference of the target gain based on the target gain.

[0016] In some embodiments, the first amplification unit includes a first resistor, a second resistor, a third resistor, a fourth resistor and a first amplifier;

[0017] The first end of the first resistor constitutes the first positive input end of the first amplifying unit connected to the negative output end of the second VGA module, the second end of the first resistor is connected to the positive input end of the first amplifier, the second resistor constitutes the second positive input end of the first amplifying unit connected to the first reference voltage, and the second end of the second resistor is connected to the positive input end of the first amplifier; the inverting input end of the first amplifier is connected to the positive output end of the second VGA module through the third resistor, and the inverting input end of the first amplifier is connected to its own output end through the fourth resistor;

[0018] Among them, R4 / R3=R2 / R1=K, wherein R1 is the resistance value of the first resistor, R2 is the resistance value of the second resistor, R3 is the resistance value of the third resistor, R4 is the resistance value of the fourth resistor, and K is the gain of the first amplifying unit.

[0019] In some embodiments, the bias voltage terminal includes a first bias voltage terminal and a second bias voltage terminal that are connected to each other, and the output terminal of the second amplifying unit is connected to the first bias voltage terminal or the second bias voltage terminal.

[0020] In some embodiments, the first VGA module and the second VGA module include:

[0021] An input stage circuit, used for receiving a differential input terminal signal;

[0022] The output stage circuit is connected to the input stage circuit and has the bias voltage terminal, and is used for gaining the voltage difference of the differential input terminal signal based on the bias voltage and then outputting the gain.

[0023] In some embodiments, the input stage circuit includes a first current source, a second current source, a first transistor, a second transistor, a degeneration resistor, and a first capacitor;

[0024] The base of the first transistor constitutes a first differential input terminal, the collector is connected to the output stage circuit, the emitter is connected to the first end of the first current source, the first end of the degeneration resistor and the first end of the first capacitor, and the second end of the first current source is grounded;

[0025] The base of the second transistor constitutes a second differential input terminal, the collector is connected to the output stage circuit, the emitter is connected to the first end of the second current source, the second end of the degeneration resistor and the second end of the first capacitor, and the second end of the second current source is grounded.

[0026] In some embodiments, the output stage circuit includes a third transistor, a fourth transistor, a fifth transistor, a sixth transistor, a first output resistor, and a second output resistor;

[0027] The base of the fourth transistor is connected to the base of the fifth transistor to form a first bias voltage terminal; the base of the third transistor is connected to the base of the sixth transistor to form a second bias voltage terminal, and the output terminal of the gain adjustment module is connected to the first bias voltage terminal or the second bias voltage terminal;

[0028] The collector of the third transistor is connected to the first end of the first output resistor to form a first differential output end, the emitter of the third transistor is connected to the input stage circuit and the emitter of the fourth transistor, and the second end of the first output resistor is connected to a working power supply;

[0029] The collector of the fourth transistor is connected to the working power supply or the collector of the sixth transistor; the collector of the fifth transistor is connected to the working power supply or the collector of the third transistor;

[0030] The collector of the sixth transistor is connected to the first end of the second output resistor to form a second differential output end, the emitter of the sixth transistor is connected to the input stage circuit and the emitter of the fifth transistor, and the second end of the second output resistor is connected to the working power supply.

[0031] Compared with the related art, the embodiments of the present application have the following beneficial effects:

[0032] The variable gain amplifier provided in the embodiment of the present application adds a sub-VGA (i.e., the second VGA module) operating at the same bias voltage to the main VGA (i.e., the first VGA module), and sets a gain adjustment module to provide a DC voltage (i.e., a differential input signal) for the sub-VGA. The gain adjustment module adjusts the bias voltage according to the deviation between the DC voltage of the actual gain and the DC voltage of the target gain to maintain the actual gain of the main VGA and the sub-VGA consistent with the target gain. In this way, even if changes in process and temperature affect the actual gain and cause deviations from the target gain, the gain adjustment module can still implement a closed-loop adjustment process of the gain deviation, thereby solving the problem that the gain of the variable gain amplifier cannot maintain stability due to process deviations and temperature changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a circuit diagram of the first type of VGA;

[0034] Figure 2 This is a circuit diagram of the second VGA;

[0035] Figure 3 A structural circuit diagram of a variable gain amplifier provided in one embodiment of the present application;

[0036] Figure 4 A circuit diagram of a variable gain amplifier provided in one embodiment of the present application;

[0037] Figure 5 A circuit diagram of a variable gain amplifier provided in accordance with an embodiment of the present application. DETAILED DESCRIPTION

[0038] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0039] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0040] It should be understood that the orientation or position relationship indicated by terms such as "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0041] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0042] like Figure 1 and Figure 2 As shown, two conventional VGA modules have two structures. The VGA (or VGA module) includes an input stage circuit 100 and an output stage circuit 200. The input stage circuit 100 is used to access the differential input terminal signal INA / INB; the output stage circuit 200 is connected to the input stage circuit 100 and has a bias voltage terminal, which is used to gain the voltage difference of the differential input terminal signal INA / INB based on the bias voltage Vbias1 / Vbias2 accessed by the bias voltage terminal and then output the gained differential output signal OUTA / OUTB.

[0043] It can be understood that the voltage difference of the differential input terminal signals INA / INB and ina / inb can be considered as a DC voltage, and its voltage value is INB-INA / inb-ina. INA / INB and ina / inb can be used to refer to: differential input terminal signal and differential input terminal at the same time, Vbias1 / Vbias2 can be used to refer to: bias voltage and bias voltage terminal at the same time, and OUTA / OUTB and outa / outb can be used to refer to: differential output signal and differential output terminal at the same time.

[0044] The input stage circuit 100 includes a first current source Isource1 , a second current source Isource2 , a first transistor T1 , a second transistor T2 , a degeneration resistor R0 , and a first capacitor C0 .

[0045] The base of the first transistor T1 forms the first differential input terminal INA, the collector of the first transistor T1 is connected to the output stage circuit 200, the emitter of the first transistor T1 is connected to the first end of the first current source Isource1, the first end of the degeneration resistor R0 and the first end of the first capacitor C0, and the second end of the first current source Isource1 is grounded. The base of the second transistor T2 forms the second differential input terminal INB, the collector of the second transistor T2 is connected to the output stage circuit 200, the emitter of the second transistor T2 is connected to the first end of the second current source Isource2, the second end of the degeneration resistor R0 and the second end of the first capacitor C0, and the second end of the second current source Isource2 is grounded.

[0046] The output stage circuit 200 includes a third transistor T3, a fourth transistor T4, a fifth transistor T5, a sixth transistor T6, a first output resistor R11, and a second output resistor R12. The base of the fourth transistor T4 is connected to the base of the fifth transistor T5 to form a first bias voltage terminal Vbias1; the base of the third transistor T3 is connected to the base of the sixth transistor T6 to form a second bias voltage terminal Vbias2. The collector of the third transistor T3 is connected to the first end of the first output resistor R11 and forms a first differential output terminal (i.e., a negative output terminal) OUTB, the emitter of the third transistor T3 is connected to the emitter of the input stage circuit 100 and the fourth transistor T4, and the second end of the first output resistor R11 is connected to the working power supply VDD.

[0047] The collector of the fourth transistor T4 is connected to the working power supply VDD (see Figure 1 ) or the collector of the sixth transistor T6 (see Figure 2 ); The collector of the fifth transistor T5 is connected to the working power supply VDD (see Figure 1 ) or the collector of the third transistor T3 (see Figure 2 The collector of the sixth transistor T6 is connected to the first end of the second output resistor R12 to form a second differential output terminal (i.e., a positive output terminal) OUTA. The emitter of the sixth transistor T6 is connected to the input stage circuit 100 and the emitter of the fifth transistor T5. The second end of the second output resistor R12 is connected to the working power supply VDD.

[0048] and Figure 2As shown, VBias2>VBias1 is always maintained to ensure the polarity correspondence between the output and input. Conventional VGAs, regardless of their structure, change the DC current flowing through transistors T3-T6 and thus the AC current flowing through output resistors R11 / R12 (where the AC current is loaded on the DC current) by adjusting the gate voltage of transistors T3-T6 of the output stage circuit 200, i.e., the bias voltage Vbias1 / Vbias2, to achieve the function of changing the output gain. Generally, under different processes or different temperatures, the fixed bias voltage difference Vbias2-Vbias1 cannot maintain the stability of the VGA gain, resulting in changes in the VGA gain under different processes or temperatures, affecting the overall performance of the circuit.

[0049] In this regard, the present application provides a variable gain amplifier capable of maintaining a stable gain. Figure 3 A variable gain amplifier according to an embodiment of the present application includes a first VGA module 110, a second VGA module 120 and a gain adjustment module 130; wherein the differential input terminal INA / INB and the differential output terminal OUTA / OUTB of the first VGA module 110 respectively constitute the differential input terminal and the differential output terminal of the variable gain amplifier.

[0050] The bias voltage terminal VBias1 / VBais2 of the second VGA module 120 is connected to the bias voltage terminal VBias1 / VBais2 of the first VGA module 110, and is connected to the bias voltage for configuring the gain. The differential input terminal ina / inb of the second VGA module 120 is used to connect the differential input terminal signal ina / inb (pressure value: inb-ina). The second VGA module 120 is used to perform actual gain on the voltage difference (inb-ina) of the differential input terminal signal based on the bias voltage VBias1 / VBais2 and then output it.

[0051] The input end of the gain adjustment module 130 is connected to the differential output end outa / outb of the second VGA module 120, and the output end of the gain adjustment module 130 is connected to the bias voltage end VBias1 / VBais2. The gain adjustment module 130 is used to adjust the bias voltage VBias1 / VBais2 according to the deviation between the voltage difference after the actual gain and the voltage difference of the target gain, so as to maintain the actual gain of the first VGA module 110, that is, the variable gain amplifier, consistent with the target gain.

[0052] The first VGA module 110 and the second VGA module 120 have the same architecture and gain configuration. Optionally, because the second VGA module 120 does not require a large bandwidth, it can be configured with lower power consumption.

[0053] Exemplarily, the voltage difference of the differential input terminal signal ina / inb input to the second VGA module 120 is: inb-ina, and the voltage difference after actual gain output by the second VGA module 120 is (inb-ina)*FM, where FM is the actual gain of the first VGA module 110 and the second VGA module 120 under the current bias voltage VBias1 / VBais2. The voltage difference of the target gain is (inb-ina)*M, where M is the target gain of the first VGA module 110 and the second VGA module 120 under the adjusted bias voltage VBias1 / VBais2 under ideal conditions. Due to the influence of process and / or temperature changes, FM and M will be inconsistent. The gain adjustment module 130 adjusts the bias voltage VBias1 / VBais2 according to the difference between (inb-ina)*FM and (inb-ina)*M, so that the bias voltage VBias1 / VBais2 (that is, the actual gain FM) can be automatically adjusted following the process and / or temperature changes to maintain the actual gain consistent with the target gain, so that the gain of the first VGA module 110, that is, the variable gain amplifier, is stable.

[0054] In some embodiments, the gain adjustment module 130 is specifically used to:

[0055] When the voltage difference after the actual gain is greater than the voltage difference of the target gain, a first adjustment voltage is output, and the first adjustment voltage is used to adjust the bias voltage to reduce the actual gain of the variable gain amplifier. Figure 1 and Figure 2 The first adjustment voltage can be used to increase the first bias voltage Vbais1 to reduce the actual gain; it can also be used to reduce the second bias voltage Vbais2 to reduce the actual gain of the variable gain amplifier.

[0056] When the voltage difference after the actual gain is less than the voltage difference of the target gain, a second adjustment voltage is output to adjust the bias voltage to increase the actual gain. Figure 1 and Figure 2 The second adjustment voltage can be used to reduce the first bias voltage Vbais1 to increase the actual gain of the variable gain amplifier; it can also be used to increase the second bias voltage Vbais2 to increase the actual gain of the variable gain amplifier.

[0057] The low-frequency gain of the first VGA module 110 is the same as the low-frequency gain of the second VGA module 120. Thus, the gain adjustment module 130 adjusts the bias voltage according to the output of the second VGA module 120 to adjust the actual gain of the second VGA module 120 to be consistent with the target gain, which is equivalent to synchronously adjusting the actual gain of the first VGA module 110 to be consistent with the target gain with the same amplitude, that is, making the actual gain of the variable gain amplifier close to or equal to the target gain.

[0058] See also Figure 4 and Figure 5 , in some embodiments, the gain adjustment module 130 includes a first amplification unit 131 and a second amplification unit 132;

[0059] The first positive input terminal of the first amplifier unit 131 is connected to the negative output terminal outb of the second VGA module 120, and the second positive input terminal of the first amplifier unit 131 is connected to the first reference voltage VREF1; the negative input terminal of the first amplifier unit 131 is connected to the positive output terminal outa of the second VGA module 120. One of the two input terminals of the second amplifier unit 132 is connected to the output terminal of the first amplifier unit 131, and the other is connected to the second reference voltage VREF2, and the output terminal of the second amplifier unit 132 is connected to the bias voltage terminal VBias1 / VBais2.

[0060] The second reference voltage VREF2 = the voltage difference (inb-ina)*M of the differential input terminal signal ina / inb inputted by the second VGA module 120 × the gain K of the first amplifying unit 131 + the first reference voltage VREF1 .

[0061] refer to Figure 4 , Figure 5 In one embodiment, the first amplifying unit 131 includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a first amplifier AMP1 and a second amplifier AMP2;

[0062] The first end of the first resistor constitutes the first positive input end of the first amplifying unit connected to the negative output end of the second VGA module, the second end of the first resistor is connected to the positive input end of the first amplifier, the second resistor constitutes the second positive input end of the first amplifying unit connected to the first reference voltage, and the second end of the second resistor is connected to the positive input end of the first amplifier; the inverting input end of the first amplifier is connected to the positive output end of the second VGA module through the third resistor, and the inverting input end of the first amplifier is connected to its own output end through the fourth resistor;

[0063] Among them, R4 / R3=R2 / R1=K, wherein R1 is the resistance value of the first resistor, R2 is the resistance value of the second resistor, R3 is the resistance value of the third resistor, R4 is the resistance value of the fourth resistor, and K is the gain of the first amplifying unit.

[0064] The first end of the first resistor R1 constitutes the first positive input end of the first amplifier unit 131 and is connected to the negative output end outb of the second VGA module 120. The second end of the first resistor R1 is connected to the positive input end of the first amplifier AMP1. The second resistor R2 constitutes the second positive input end of the first amplifier unit 131 and is connected to the first reference voltage VREF1. The second end of the second resistor R2 is connected to the positive input end of the first amplifier AMP1. The inverting input end of the first amplifier AMP1 is connected to the positive output end outa of the second VGA module 120 through the third resistor R3. The inverting input end of the first amplifier AMP1 is also connected to its own output end VOUT1 through the fourth resistor R4. The second amplifier unit 132 includes a second amplifier AMP2.

[0065] refer to Figures 3 to 5 In one embodiment, the bias voltage terminal VBias1 / VBais2 includes a first bias voltage terminal VBias1 and a second bias voltage terminal VBais2 connected to each other, and the output terminal of the second amplifier AMP2 is connected to the first bias voltage terminal VBias1 or the second bias voltage terminal VBais2. Specifically:

[0066] refer to Figure 4 In one embodiment, the non-inverting input terminal of the second amplifier AMP2 is connected to the output terminal VOUT1 of the first amplifier AMP1, the inverting input terminal of the second amplifier AMP2 is connected to the second reference voltage VREF2, and the output terminal of the second amplifier AMP2 is connected to the first bias voltage terminal VBias1.

[0067] refer to Figure 5 In one embodiment, the non-inverting input terminal of the second amplifier AMP2 is connected to the second reference voltage VREF2, the inverting input terminal of the second amplifier AMP2 is connected to the output terminal VOUT1 of the first amplifier AMP1, and the output terminal of the second amplifier AMP2 is connected to the first bias voltage terminal VBias2.

[0068] In one embodiment, the gain adjustment module 130 also includes a voltage source U0, which is connected to the non-inverting input terminal or the inverting input terminal of the second amplifier AMP2. The voltage source U0 includes a gain setting terminal, which is used to set the target gain M according to the differential input terminal signal ina / inb input by the second VGA module 120. The voltage source U0 is used to provide a target gain voltage difference based on the set target gain M: (inb-ina)*M*K.

[0069] Among them, R4 / R3=R2 / R1=K, R1 is the resistance value of the first resistor R1, R2 is the resistance value of the second resistor R2, R3 is the resistance value of the third resistor R3, R4 is the resistance value of the fourth resistor R4, and K is the gain of the first amplifying unit 131. Exemplarily, the first resistor R1 and the third resistor R3 are the first resistance values; the second resistor R2 and the fourth resistor R4 are the second resistance values, and the second resistance value is K times the first resistance value. As a result, the gain of the output of the first amplifying unit 131 relative to the input is K, that is, the output of the first amplifier AMP1 is (inb-ina)*FM*K+VREF1. It can be understood that the gain K is the gain of the fixed ratio amplifier formed by the first amplifier AMP1 and the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4.

[0070] by Figure 4 Taking the gain adjustment module 130 as an example, a differential input signal with a DC voltage difference of (inb-ina) is given at the input of the second VGA module 120. If the actual gain of the second VGA module 120 is FM at this time, the output of the second VGA module 120 is (inb-ina)*FM. The voltage output from the first amplifier AMP1 to the non-inverting input terminal of the second amplifier AMP2 is (inb-ina)*FM*K+VREF1, and the second reference voltage VREF2 connected to the inverting input terminal of the second amplifier AMP2 is (inb-ina)*M*K+VREF1. Among them, the voltage source U0 configures an output voltage of (inb-ina)*M*K based on the input DC voltage (inb-ina) and the target gain M, and gives it to the inverting input terminal of the second amplifier AMP2.

[0071] Combination Figure 1 , 2 and Figure 4 , if (inb-ina)*FM*K+VREF1>(inb-ina)*M*K+VREF1, the voltage outputted by the second amplifier AMP2 to the first bias voltage terminal VBias1 becomes larger, Figure 1 and Figure 2 It can be seen that the actual gain FM of the first VGA module 110 and the second VGA module 120 decreases until it is close to or equal to M. If (inb-ina)*FM*K+VREF1<(inb-ina)*M*K+VREF1, the voltage output by the second amplifier AMP2 to the first bias voltage terminal VBias1 decreases, and the actual gain FM of the first VGA module 110 and the second VGA module 120 increases until it is close to or equal to M. Thus, the gain stability of the variable gain amplifier is maintained without changing with process and temperature changes.

[0072] Please continue reading Figure 1 and Figure 2 In one embodiment, the first VGA module 110 and the second VGA module 120 include:

[0073] The input stage circuit 100 is used to access the differential input terminal signal INA / INB;

[0074] The output stage circuit 200 is connected to the input stage circuit 100 and has a bias voltage terminal VBias1 / VBais2, which is used to gain the voltage difference of the differential input terminal signal based on the bias voltage VBias1 / VBais2 and then output the gained differential output signal OUTA / OUTB.

[0075] The input stage circuit 100 includes a first current source Isource1, a second current source Isource2, a first transistor T1, a second transistor T2, a degeneration resistor R0 and a first capacitor C0;

[0076] The base of the first transistor T1 forms a first differential input terminal INA / ina, the collector of the first transistor T1 is connected to the output stage circuit 200, the emitter of the first transistor T1 is connected to the first end of the first current source Isource1, the first end of the degeneration resistor R0 and the first end of the first capacitor C0, and the second end of the first current source Isource1 is grounded. The base of the second transistor T2 forms a second differential input terminal INB / inb, the collector of the second transistor T2 is connected to the output stage circuit 200, the emitter of the second transistor T2 is connected to the first end of the second current source Isource2, the second end of the degeneration resistor R0 and the second end of the first capacitor C0, and the second end of the second current source Isource2 is grounded.

[0077] The output stage circuit 200 includes a third transistor T3, a fourth transistor T4, a fifth transistor T5, a sixth transistor T6, a first output resistor R11 and a second output resistor R12.

[0078] The base of the fourth transistor T4 is connected to the base of the fifth transistor T5 to form a first bias voltage terminal VBias1; the base of the third transistor T3 is connected to the base of the sixth transistor T6 to form a second bias voltage terminal VBais2, and the output terminal of the gain adjustment module 130 is connected to the first bias voltage terminal VBias1, see Figure 4 Or, the output terminal of the gain adjustment module 130 is connected to the second bias voltage terminal VBais2, see Figure 5 .

[0079] The collector of the third transistor T3 is connected to the first end of the first output resistor R11, and constitutes the first differential output end (i.e., the negative output end) OUTB / outb. The emitter of the third transistor T3 is connected to the input stage circuit 100 and the emitter of the fourth transistor T4. The second end of the first output resistor R11 is connected to the working power supply VDD.

[0080] The collector of the fourth transistor T4 is connected to the working power supply VDD (see Figure 1 ) or the collector of the sixth transistor T6 (see Figure 2 ); The collector of the fifth transistor T5 is connected to the working power supply VDD (see Figure 1 ) or the collector of the third transistor T3 (see Figure 2 The collector of the sixth transistor T6 is connected to the first end of the second output resistor R12 to form a second differential output terminal (i.e., a positive output terminal) OUTA / outa. The emitter of the sixth transistor T6 is connected to the input stage circuit 100 and the emitter of the fifth transistor T5. The second end of the second output resistor R12 is connected to the working power supply VDD.

[0081] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A variable gain amplifier, characterized in that: It comprises a first VGA module, a second VGA module and a gain adjustment module, wherein the differential input end and the differential output end of the first VGA module respectively constitute the differential input end and the differential output end of the variable gain amplifier; The bias voltage terminal of the second VGA module is connected to the bias voltage terminal of the first VGA module and is connected to a bias voltage for configuring gain. The differential input terminal of the second VGA module is used to connect a differential input terminal signal. The second VGA module is used to perform actual gain on the voltage difference of the differential input terminal signal based on the bias voltage and then output it. The input end of the gain adjustment module is connected to the differential output end of the second VGA module, and the output end of the gain adjustment module is connected to the bias voltage end. The gain adjustment module is used to adjust the bias voltage according to the deviation between the voltage difference after actual gain and the voltage difference of target gain, so as to maintain the actual gain of the first VGA module consistent with the target gain.

2. The variable gain amplifier according to claim 1, wherein: The gain adjustment module is specifically used for: When the voltage difference after the actual gain is greater than the voltage difference of the target gain, outputting a first regulating voltage, wherein the first regulating voltage is used to adjust the bias voltage to reduce the actual gain; In the case where the voltage difference after actual gain is less than the voltage difference after target gain, a second regulating voltage is output to regulate the bias voltage to increase the actual gain.

3. The variable gain amplifier according to claim 1, wherein: The low-frequency gain of the first VGA module is the same as the low-frequency gain of the second VGA module.

4. The variable gain amplifier according to any one of claims 1 to 3, characterized in that: The gain adjustment module includes a first amplification unit and a second amplification unit; The first positive input terminal of the first amplifying unit is connected to the negative output terminal of the second VGA module, and the second positive input terminal of the first amplifying unit is connected to the first reference voltage; the inverting input terminal of the first amplifying unit is connected to the positive output terminal of the second VGA module; One of the two input terminals of the second amplifying unit is connected to the output terminal of the first amplifying unit, and the other is connected to a second reference voltage, and the output terminal of the second amplifying unit is connected to the bias voltage terminal; The second reference voltage=the voltage difference of the target gain×the gain of the first amplifying unit+the first reference voltage.

5. The variable gain amplifier according to claim 4, wherein: The gain adjustment module further includes a voltage source, which is connected to the second amplifying unit. The voltage source includes a gain setting terminal for setting the target gain, and the voltage source is used to provide the voltage difference of the target gain based on the target gain.

6. The variable gain amplifier according to claim 4, wherein: The first amplifying unit includes a first resistor, a second resistor, a third resistor, a fourth resistor and a first amplifier; The first end of the first resistor constitutes the first positive input end of the first amplifying unit connected to the negative output end of the second VGA module, the second end of the first resistor is connected to the positive input end of the first amplifier, the second resistor constitutes the second positive input end of the first amplifying unit connected to the first reference voltage, and the second end of the second resistor is connected to the positive input end of the first amplifier; the inverting input end of the first amplifier is connected to the positive output end of the second VGA module through the third resistor, and the inverting input end of the first amplifier is connected to its own output end through the fourth resistor; Among them, R4 / R3=R2 / R1=K, wherein R1 is the resistance value of the first resistor, R2 is the resistance value of the second resistor, R3 is the resistance value of the third resistor, R4 is the resistance value of the fourth resistor, and K is the gain of the first amplifying unit.

7. The variable gain amplifier according to claim 4, wherein: The bias voltage terminal includes a first bias voltage terminal and a second bias voltage terminal that are connected to each other, and the output terminal of the second amplifying unit is connected to the first bias voltage terminal or the second bias voltage terminal.

8. The variable gain amplifier according to any one of claims 1 to 3, characterized in that: The first VGA module and the second VGA module include: An input stage circuit, used for receiving a differential input terminal signal; The output stage circuit is connected to the input stage circuit and has the bias voltage terminal, and is used for gaining the voltage difference of the differential input terminal signal based on the bias voltage and then outputting the gain.

9. The variable gain amplifier according to claim 8, wherein: The input stage circuit includes a first current source, a second current source, a first transistor, a second transistor, a degeneration resistor and a first capacitor; The base of the first transistor constitutes a first differential input terminal, the collector is connected to the output stage circuit, the emitter is connected to the first end of the first current source, the first end of the degeneration resistor and the first end of the first capacitor, and the second end of the first current source is grounded; The base of the second transistor constitutes a second differential input terminal, the collector is connected to the output stage circuit, the emitter is connected to the first end of the second current source, the second end of the degeneration resistor and the second end of the first capacitor, and the second end of the second current source is grounded.

10. The variable gain amplifier according to claim 8, wherein: The output stage circuit includes a third transistor, a fourth transistor, a fifth transistor, a sixth transistor, a first output resistor and a second output resistor; The base of the fourth transistor is connected to the base of the fifth transistor to form a first bias voltage terminal; the base of the third transistor is connected to the base of the sixth transistor to form a second bias voltage terminal, and the output terminal of the gain adjustment module is connected to the first bias voltage terminal or the second bias voltage terminal; The collector of the third transistor is connected to the first end of the first output resistor to form a first differential output end, the emitter of the third transistor is connected to the input stage circuit and the emitter of the fourth transistor, and the second end of the first output resistor is connected to a working power supply; The collector of the fourth transistor is connected to the working power supply or the collector of the sixth transistor; the collector of the fifth transistor is connected to the working power supply or the collector of the third transistor; The collector of the sixth transistor is connected to the first end of the second output resistor to form a second differential output end, the emitter of the sixth transistor is connected to the input stage circuit and the emitter of the fifth transistor, and the second end of the second output resistor is connected to the working power supply.

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