A source follower voltage mismatch adjustment circuit

Abstract

The application discloses a kind of source follower voltage mismatch adjustment circuit, it is related to the field of source follower, including first source follower module, second source follower module and closed loop feedback module, wherein first source follower module is used to receive input voltage, second source follower module is used to receive the output voltage of first source follower module, and sends output voltage to outside, closed loop feedback module is used to receive and compare the input voltage of first source follower module and the output voltage of second source follower module, according to the comparison result generates feedback signal and sends to second source follower module, and second source follower module is used to force the direct current level of the input voltage of first source follower module and the output voltage of second source follower module consistent according to feedback signal.The application realizes the direct current level of the output voltage and input voltage of source follower consistent by the way of closed loop feedback.

Description

Technical Field

[0001] This invention relates to the field of source followers, and in particular to a source follower voltage mismatch adjustment circuit. Background Technology

[0002] In electronic systems, common source amplifiers are often used as output driver stages because of their low output impedance and large bandwidth; they are also known as source followers.

[0003] In existing technologies, there are source followers based on NMOS transistors and source followers based on PMOS transistors. Their characteristic is that the output voltage follows the change of the input voltage, and they have good AC following characteristics and linearity. However, due to the inherent voltage difference between the gate and source of the NMOS and PMOS transistors when they are turned on, the DC level of the output voltage and the input voltage are not consistent. For a source follower based on an NMOS transistor, the output voltage = input voltage - voltage difference; for a source follower based on a PMOS transistor, the output voltage = input voltage + voltage difference.

[0004] In existing technologies, when the DC level of the output voltage needs to match the DC level of the input voltage, a complementary structure is required. This involves using both an NMOS-based source follower and a PMOS-based source follower simultaneously. The output voltage is equal to the input voltage by either first decreasing the input voltage by a differential voltage and then increasing it by an equal differential voltage, or vice versa. However, in engineering practice, due to the inherent threshold voltage difference between NMOS and PMOS transistors, and mismatch issues during manufacturing, the increased and decreased differential voltages may not be equal, leading to a difference in the DC levels of the output and input voltages. Therefore, there is a pressing need to design a source follower voltage mismatch adjustment circuit to address the problem of DC level discrepancies between the output and input voltages caused by existing source followers. Summary of the Invention

[0005] The purpose of this invention is to provide a source follower voltage mismatch adjustment circuit that achieves the same DC level between the output voltage and the input voltage of the source follower through closed-loop feedback.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] A source follower voltage mismatch adjustment circuit includes:

[0008] The first source follower module is used to receive the input voltage;

[0009] The second source follower module is connected to the first source follower module and is used to receive the output voltage of the first source follower module and send the output voltage to the outside.

[0010] A closed-loop feedback module is connected to the first source follower module and the second source follower module respectively, and is used to receive and compare the input voltage and the output voltage, generate a feedback signal based on the comparison result and send it to the second source follower module;

[0011] The second source follower module is also used to force the DC levels of the input voltage and the output voltage to be the same according to the feedback signal.

[0012] Optionally, the first source follower module includes: a first source follower transistor and a first current bias transistor;

[0013] The drain of the first source follower transistor is connected to the power supply, the gate of the first source follower transistor is connected to the input voltage and the closed-loop feedback module, the source of the first source follower transistor is connected to the drain of the first current bias transistor and the second source follower module, the gate of the first current bias transistor is connected to the first bias voltage, and the source of the first current bias transistor is grounded.

[0014] Optionally, the second source follower module includes: a second source follower transistor and a second current bias transistor;

[0015] The drain of the second source follower transistor is grounded, the gate of the second source follower transistor is connected to the source of the first source follower transistor and the closed-loop feedback module, the source of the second source follower transistor is connected to the drain of the second current bias transistor and the closed-loop feedback module respectively; the gate of the second current bias transistor is connected to the second bias voltage, and the source of the second current bias transistor is connected to the power supply.

[0016] Optionally, the closed-loop feedback module includes: an operational amplifier, a filter, and a current compensation transistor;

[0017] The inverting input of the operational amplifier is connected to the gate of the first source follower transistor, the non-inverting input of the operational amplifier is connected to the source of the second source follower transistor, the output of the operational amplifier is connected to one end of the filter, the other end of the filter is connected to the gate of the current compensation transistor, the drain of the current compensation transistor is connected to the gate of the second source follower transistor, and the source of the current compensation transistor is grounded.

[0018] Optionally, the first source follower transistor, the first current bias transistor, and the current compensation transistor are all NMOS field-effect transistors; the second source follower transistor and the second current bias transistor are both PMOS field-effect transistors.

[0019] Optionally, the operational amplifier is a two-stage operational amplifier.

[0020] Optionally, the filter is a passive RC filter.

[0021] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0022] The source follower voltage mismatch adjustment circuit provided by the present invention employs a two-stage source follower. By setting up a closed-loop feedback module, it receives and compares the input voltage of the first source follower module and the output voltage of the second source follower module. Based on the comparison result, a feedback signal is generated and sent to the second source follower module. The feedback signal forces the DC levels of the input voltage and the output voltage to be consistent. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a circuit diagram of an existing source follower based on NMOS transistors;

[0025] Figure 2 The circuit diagram is for an existing source follower implemented using a PMOS transistor.

[0026] Figure 3 This is a circuit diagram of a complementary source follower implemented using NMOS and PMOS transistors.

[0027] Figure 4 This is a complementary circuit diagram of a source follower implemented using NMOS and PMOS transistors.

[0028] Figure 5 A circuit diagram of the source follower voltage mismatch adjustment circuit provided by the present invention;

[0029] Figure 6 A circuit diagram of an operational amplifier provided by the present invention;

[0030] Figure 7 A circuit diagram of the filter provided by the present invention. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] like Figure 1 and Figure 2 As shown, existing source followers based on NMOS transistors and source followers based on PMOS transistors have inconsistent DC levels between the output voltage and the input voltage due to the inherent voltage difference between the gate and source when the NMOS and PMOS transistors are turned on.

[0033] like Figure 3 and Figure 4 As shown, existing source followers that simultaneously use one NMOS transistor-based source follower and one PMOS transistor-based source follower achieve the effect of output voltage equal to input voltage by first decreasing the input voltage by a differential voltage and then increasing it by an equal differential voltage, or by first increasing the input voltage by a differential voltage and then decreasing it by an equal differential voltage. However, due to the inherent threshold voltage difference between NMOS and PMOS transistors, and mismatch issues during manufacturing, the increased and decreased differential voltages may not be equal, resulting in a difference in the DC level between the output and input voltages.

[0034] The purpose of this invention is to provide a source follower voltage mismatch adjustment circuit that achieves the same DC level between the output voltage and the input voltage of the source follower through closed-loop feedback.

[0035] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] The source follower voltage mismatch adjustment circuit provided by the present invention includes: a first source follower module, a second source follower module, and a closed-loop feedback module.

[0037] The first source follower module is used to receive the input voltage; the second source follower module is connected to the first source follower module and is used to receive the output voltage of the first source follower module and send the output voltage to the outside; the closed-loop feedback module is connected to the first source follower module and the second source follower module respectively, and is used to receive and compare the input voltage and the output voltage, generate a feedback signal according to the comparison result and send it to the second source follower module; the second source follower module is also used to force the DC level of the input voltage and the output voltage to be consistent according to the feedback signal.

[0038] like Figure 5 As shown, the first source follower module includes: a first source follower transistor M1 and a first current bias transistor M2; the drain of the first source follower transistor M1 is connected to the power supply, the gate of the first source follower transistor M1 is connected to the input voltage Vin and the closed-loop feedback module respectively, and the source of the first source follower transistor M1 is connected to the drain of the first current bias transistor M2 and the second source follower module respectively; the gate of the first current bias transistor M2 is connected to the first bias voltage V. BN The source of the first current-biasing transistor M2 is grounded. The first current-biasing transistor M2 provides bias current to the first source-follower transistor M1. Both the first source-follower transistor M1 and the first current-biasing transistor M2 are NMOS field-effect transistors.

[0039] like Figure 5 As shown, the second source follower module includes: a second source follower transistor M3 and a second current bias transistor M4; the drain of the second source follower transistor M3 is grounded, the gate of the second source follower transistor M3 is connected to the source of the first source follower transistor M1 and the closed-loop feedback module, and the source of the second source follower transistor M3 is connected to the drain of the second current bias transistor M4 and the closed-loop feedback module; the gate of the second current bias transistor M4 is connected to a second bias voltage, and the source of the second current bias transistor M4 is connected to a power supply. The second current bias transistor M4 provides bias current to the second source follower transistor M3. Both the second source follower transistor M3 and the second current bias transistor M4 are PMOS field-effect transistors.

[0040] like Figure 5As shown, the closed-loop feedback module includes: operational amplifier A, filter XY, and current compensation transistor M0. The inverting input of operational amplifier A is connected to the gate of the first source follower transistor M1, the non-inverting input of operational amplifier A is connected to the source of the second source follower transistor M3, and the output of operational amplifier A is connected to one end of filter XY. The other end of filter XY is connected to the gate of current compensation transistor M0. The drain of current compensation transistor M0 is connected to the gate of the second source follower transistor M3, and the source of current compensation transistor M0 is grounded. The error signal generated by the inverting and non-inverting inputs of operational amplifier A is input to the gate of current compensation transistor M0 after passing through filter XY. The transconductance of current compensation transistor M0 converts the signal into a drain current, which is the feedback signal. Current compensation transistor M0 is an NMOS field-effect transistor. The function of filter XY is to ensure that the circuit of the closed-loop feedback module only works on low-frequency signals near the DC level, and the loop bandwidth is much lower than the signal bandwidth, thereby ensuring that the AC level tracking effect of the source follower voltage mismatch adjustment circuit itself is not affected.

[0041] Furthermore, when the input voltage Vin > the output voltage Vout, the output voltage of operational amplifier A decreases. This reduces the current of the current compensation transistor M0, causing a decrease in the current of the first source follower transistor M1. The voltage difference decreases, meaning the source voltage of the first source follower transistor M1 increases, thus increasing the output voltage Vout. When the gain of operational amplifier A is sufficiently large, the system will stabilize at the position where the output voltage Vout = the input voltage Vin. Conversely, when the input voltage Vin < the output voltage Vout, the output voltage of operational amplifier A increases. This increases the current of the current compensation transistor M0, causing an increase in the current of the first source follower transistor M1. The voltage difference increases, meaning the source voltage of the first source follower transistor M1 decreases, thus decreasing the output voltage Vout. When the gain of operational amplifier A is sufficiently large, the system will stabilize at the position where the output voltage Vout = the input voltage Vin.

[0042] Furthermore, such as Figure 6 As shown, operational amplifier A is a two-stage operational amplifier. Transistor M... A1 and transistor M A2 It is the first-stage transconductance device of operational amplifier A, transistor M. A0 Transistor M provides bias current as its common tail current source. A1 Transistor M A2 and transistor M A0 All are NMOS transistors. Transistor M A5 and transistor M A6 It is the second-stage transconductance device of operational amplifier A, transistor M. A3It is transistor M A1 Active load, transistor M A4 It is transistor M A2 The active load, the output terminals of the first-stage transconductance devices are transistors M and M respectively. A5 and transistor M A6 Gate connection, transistor M A5 Transistor M A6 Transistor M A3 and transistor M A4 All are PMOS transistors. Transistor M A8 It is transistor M A6 Active load, transistor M A7 It is transistor M A5 The active load. Among them, transistor M... A7 and transistor M A8 The constructed current mirror structure also converts the differential output structure generated by the second-stage transconductance device into a single-ended output structure from transistor M. A8 The drain output.

[0043] Furthermore, such as Figure 7 As shown, filter XY is a passive RC filter, consisting of resistor R and capacitor C.

[0044] This invention provides a source follower voltage mismatch adjustment circuit that employs a two-stage source follower. A closed-loop feedback module receives and compares the input voltage of the first source follower module and the output voltage of the second source follower module. Based on the comparison result, a feedback signal is generated and sent to the second source follower module. This feedback signal forces the DC levels of the input and output voltages to be consistent, automatically eliminating DC level errors without affecting the high-frequency operating characteristics of the source follower. This source follower voltage mismatch adjustment circuit is also applicable to emitter follower circuits in transistor circuits.

[0045] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0046] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the circuit and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A source follower voltage mismatch adjustment circuit, characterized in that, include: The first source follower module is used to receive the input voltage; The first source follower module includes: a first source follower transistor and a first current bias transistor; The drain of the first source follower transistor is connected to the power supply, the gate of the first source follower transistor is connected to the input voltage and the closed-loop feedback module respectively, and the source of the first source follower transistor is connected to the drain of the first current bias transistor and the second source follower module respectively; the gate of the first current bias transistor is connected to the first bias voltage, and the source of the first current bias transistor is grounded. The second source follower module is connected to the first source follower module and is used to receive the output voltage of the first source follower module and send the output voltage to the outside. The second source follower module includes: a second source follower transistor and a second current bias transistor; The drain of the second source follower transistor is grounded, the gate of the second source follower transistor is connected to the source of the first source follower transistor and the closed-loop feedback module, and the source of the second source follower transistor is connected to the drain of the second current bias transistor and the closed-loop feedback module respectively; the gate of the second current bias transistor is connected to the second bias voltage, and the source of the second current bias transistor is connected to the power supply. A closed-loop feedback module is connected to the first source follower module and the second source follower module respectively, and is used to receive and compare the input voltage and the output voltage, generate a feedback signal based on the comparison result and send it to the second source follower module; The second source follower module is also used to force the DC levels of the input voltage and the output voltage to be the same according to the feedback signal.

2. The source follower voltage mismatch adjustment circuit according to claim 1, characterized in that, The closed-loop feedback module includes: an operational amplifier, a filter, and a current compensation transistor; The inverting input of the operational amplifier is connected to the gate of the first source follower transistor, the non-inverting input of the operational amplifier is connected to the source of the second source follower transistor, the output of the operational amplifier is connected to one end of the filter, the other end of the filter is connected to the gate of the current compensation transistor, the drain of the current compensation transistor is connected to the gate of the second source follower transistor, and the source of the current compensation transistor is grounded.

3. The source follower voltage mismatch adjustment circuit according to claim 2, characterized in that, The first source follower transistor, the first current bias transistor, and the current compensation transistor are all NMOS field-effect transistors; the second source follower transistor and the second current bias transistor are both PMOS field-effect transistors.

4. The source follower voltage mismatch adjustment circuit according to claim 2, characterized in that, The operational amplifier is a two-stage operational amplifier.

5. The source follower voltage mismatch adjustment circuit according to claim 2, characterized in that, The filter is a passive RC filter.

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