阅读说明：本技术 一种单端输出的低噪声全差分开关电容滤波器 (Single-ended output low-noise fully-differential switch capacitor filter ) 是由 李恒 王磊 于 2020-05-18 设计创作，主要内容包括：本发明提出一种单端输出的低噪声全差分开关电容滤波器,通过将双端转单端电路内置在全差分开关电容滤波器的环路内,所述双端转单端电路的输出端通过开关管与全差分开关电容滤波器的反馈电容对相连。本发明的结构不仅能实现传统的双端转单端输出的功能,还能实现抑制双端转单端电路的噪声和失配影响、以及slew rate带来的信号非线性。(The invention provides a single-ended output low-noise fully-differential switched capacitor filter, wherein a double-end-to-single-end circuit is arranged in a loop of the fully-differential switched capacitor filter, and the output end of the double-end-to-single-end circuit is connected with a feedback capacitor pair of the fully-differential switched capacitor filter through a switch tube. The structure of the invention can not only realize the function of traditional double-end-to-single-end output, but also inhibit the noise and mismatch influence of the double-end-to-single-end circuit and the signal nonlinearity brought by the slew rate.)

1. The low-noise fully-differential switched capacitor filter with single-ended output is characterized in that a double-end-to-single-ended circuit is arranged in a loop of the fully-differential switched capacitor filter, and an output end of the double-end-to-single-ended circuit is connected with a feedback capacitor pair of the fully-differential switched capacitor filter through a switch tube.

2. The single-ended output low-noise fully-differential switched-capacitor filter according to claim 1, wherein a buffer is provided between the output terminal of the double-ended to single-ended circuit and the switch tube, and the buffer is composed of a resistor capacitor or an operational amplifier.

3. The single-ended output low noise fully differential switched capacitor filter of claim 1, comprising: the circuit comprises a signal source, a square wave generator, a fully differential amplifier (128), a differential amplifier (124), 1 pair of sampling capacitors, 1 pair of feedback capacitors, 1 pair of integrating capacitors, 6 pairs of switching tubes, 4 resistors and 2 capacitors, wherein the 6 pairs of switching tubes are connected with the square wave generator;

the signal source comprises an input signal source (119) and a direct current bias voltage source (120), the input signal source (119) and the direct current bias voltage source (120) are sequentially connected, and the other end of the direct current bias voltage source (120) is grounded;

one end of a ninth switching tube (101) is connected with an input signal source (119) to obtain an input signal, the other end of the ninth switching tube (101) is connected with one end of a third switching tube (107) and one end of a first sampling capacitor (103) in a common mode, and the other end of the third switching tube (107) is grounded; the other end of the first sampling capacitor (103) is connected with one end of a first switch tube (108), one end of a seventh switch tube (104) and one end of a first feedback capacitor (102) in common, and the other end of the first switch tube (108) is grounded; the other end of the seventh switch tube (104) and one end of the first integrating capacitor (114) are both connected with the inverting input end of the fully differential amplifier (128), and the other end of the first integrating capacitor (114) and one end of the first resistor (121) are both connected with the non-inverting output end of the fully differential amplifier (128); the other end of the first resistor (121), one end of the second resistor (122) and one end of the first capacitor (123) are connected with the inverting input end of the differential amplifier (124), the other end of the second resistor (122) and the other end of the first capacitor (123) are connected with the output end of the differential amplifier (124), and the output end of the differential amplifier (124) is used as the output end of the single-ended output low-noise fully-differential switched capacitor filter;

the other end of the first feedback capacitor (102) is connected with one end of an eleventh switching tube (105) and one end of a fifth switching tube (106) in common, and the other end of the fifth switching tube (106) is grounded; the other end of the eleventh switching tube (105) and one end of the sixth switching tube (115) are connected with the output end of the differential amplifier (124);

one end of a tenth switching tube (118) is connected with a direct-current bias voltage source (120) to obtain an input signal, the other end of the tenth switching tube (118) is connected with one end of a fourth switching tube (109) and one end of a second sampling capacitor (116) in a common mode, and the other end of the fourth switching tube (109) is grounded; the other end of the second sampling capacitor (116) is connected with one end of the second switch tube (110), one end of the eighth switch tube (117) and one end of the second feedback capacitor (112) in common, and the other end of the second switch tube (110) is grounded; the other end of the eighth switching tube (117) and one end of the second integrating capacitor (111) are both connected with the non-inverting input end of the fully differential amplifier (128), and the other end of the second integrating capacitor (111) and one end of the fourth resistor (127) are both connected with the inverting output end of the fully differential amplifier (128); the other end of the fourth resistor (127), one end of the third resistor (126) and one end of the second capacitor (125) are connected with the non-inverting input end of the differential amplifier (124), and the other end of the third resistor (126) and the other end of the second capacitor (125) are grounded;

the other end of the second feedback capacitor (112) is commonly connected with one end of a twelfth switching tube (113) and the other end of a sixth switching tube (115), and the other end of the twelfth switching tube (113) is grounded.

4. The single-ended output low noise fully differential switched capacitor filter of claim 2, comprising: the circuit comprises a signal source, a square wave generator, a fully differential amplifier (128), a differential amplifier (124), 1 pair of sampling capacitors, 1 pair of feedback capacitors, 1 pair of integrating capacitors, 6 pairs of switching tubes, 5 resistors and 3 capacitors, wherein the 6 pairs of switching tubes are connected with the square wave generator;

the signal source comprises an input signal source (119) and a direct current bias voltage source (120), the input signal source (119) and the direct current bias voltage source (120) are sequentially connected, and the other end of the direct current bias voltage source (120) is grounded;

one end of a ninth switching tube (101) is connected with an input signal source (119) to obtain an input signal, the other end of the ninth switching tube (101) is connected with one end of a third switching tube (107) and one end of a first sampling capacitor (103) in a common mode, and the other end of the third switching tube (107) is grounded; the other end of the first sampling capacitor (103) is connected with one end of a first switch tube (108), one end of a seventh switch tube (104) and one end of a first feedback capacitor (102) in common, and the other end of the first switch tube (108) is grounded; the other end of the seventh switch tube (104) and one end of the first integrating capacitor (114) are both connected with the inverting input end of the fully differential amplifier (128), and the other end of the first integrating capacitor (114) and one end of the first resistor (121) are both connected with the non-inverting output end of the fully differential amplifier (128); the other end of the first resistor (121), one end of the second resistor (122) and one end of the first capacitor (123) are connected with the inverting input end of the differential amplifier (124), the other end of the second resistor (122) and the other end of the first capacitor (123) are connected with the output end of the differential amplifier (124), and the output end of the differential amplifier (124) is used as the output end of the single-ended output low-noise fully-differential switched capacitor filter;

the other end of the first feedback capacitor (102) is connected with one end of an eleventh switching tube (105) and one end of a fifth switching tube (106) in common, and the other end of the fifth switching tube (106) is grounded; the other end of the eleventh switching tube (105) is connected with one end of a third capacitor (130), one end of a fifth resistor (129) and one end of a sixth switching tube (115) in common, the other end of the third capacitor (130) is grounded, and the other end of the fifth resistor (129) is connected with the output end of the differential amplifier (124);

one end of a tenth switching tube (118) is connected with a direct-current bias voltage source (120) to obtain an input signal, the other end of the tenth switching tube (118) is connected with one end of a fourth switching tube (109) and one end of a second sampling capacitor (116) in a common mode, and the other end of the fourth switching tube (109) is grounded; the other end of the second sampling capacitor (116) is connected with one end of the second switch tube (110), one end of the eighth switch tube (117) and one end of the second feedback capacitor (112) in common, and the other end of the second switch tube (110) is grounded; the other end of the eighth switching tube (117) and one end of the second integrating capacitor (111) are both connected with the non-inverting input end of the fully differential amplifier (128), and the other end of the second integrating capacitor (111) and one end of the fourth resistor (127) are both connected with the inverting output end of the fully differential amplifier (128); the other end of the fourth resistor (127), one end of the third resistor (126) and one end of the second capacitor (125) are connected with the non-inverting input end of the differential amplifier (124), and the other end of the third resistor (126) and the other end of the second capacitor (125) are grounded;

the other end of the second feedback capacitor (112) is commonly connected with one end of a twelfth switching tube (113) and the other end of a sixth switching tube (115), and the other end of the twelfth switching tube (113) is grounded.

5. The single-ended output low-noise fully-differential switched capacitor filter according to claim 3 or 4, wherein the first switch tube (108) and the second switch tube (110) are controlled by a first timing sequence (131), the third switch tube (107), the fourth switch tube (109), the fifth switch tube (106) and the sixth switch tube (115) are controlled by a second timing sequence (132), and the falling edge of the second timing sequence (132) is later than that of the first timing sequence (131);

the seventh switch tube (104) and the eighth switch tube (117) are controlled by a third time sequence (133), the ninth switch tube (101), the tenth switch tube (118), the eleventh switch tube (105) and the twelfth switch tube (113) are controlled by a fourth time sequence (134), and the falling edge of the fourth time sequence (134) is later than that of the third time sequence (133);

the first timing (131), the second timing (132), the third timing (133), and the fourth timing (134) are non-overlapping with each other.

6. The single-ended output low-noise fully-differential switched-capacitor filter according to claim 3 or 4, wherein the capacitance of the feedback capacitor pair is half of the original value.

7. The single-ended output low-noise fully-differential switched-capacitor filter according to claim 3 or 4, wherein the capacitance of the sampling capacitor pair is twice that of the original.

Technical Field

The invention relates to acquisition, amplification and analog-to-digital conversion (ADC) of sensors and other physical signals, which is suitable for a high-sensitivity signal link system, especially for signal acquisition and conditioning of a weak signal sensor, and has wide applicability in the fields of automobiles, household appliances, industrial automation, robots, Internet of things and military industry.

Background

In order to obtain a single-ended signal from the double-ended output signal of a switched capacitor filter, the conventional approach is shown in fig. 1. The double-ended output of the fully differential switched capacitor filter (SCF is shown as a 1 st order low pass filter, but is not limited thereto) is directly connected to a double-to-single ended circuit to achieve the desired requirements.

Wherein 119 is an input signal, and 120 is an input dc bias voltage;

128 is a fully differential amplifier, 124 is a differential amplifier;

114, 111 is the integration capacitance of the SCF;

103, 116 is an input stage sampling capacitor of the SCF;

102, 112 is the feedback capacitance of the SCF;

108, 110 are switch components of the SCF and are controlled by 131 time sequences in the timing diagram;

107, 109, 106, 115 are switch components of the SCF, controlled by the 132 timing in the timing diagram, in order to avoid the influence of charge injection on the signal when the switch is turned off, the falling edge of the 132 timing is later than that of the 131 timing;

104, 117 are switch components of SCF, controlled by 133 timing in the timing diagram;

101, 118, 105, 113 are switch components of SCF, controlled by 134 timing in the timing diagram, where the falling edge of 134 timing is later than 133 timing in order to avoid the influence of charge injection on the signal when the switch is turned off;

the sequences 133 and 134 and the sequences 131 and 132 are non-overlapping.

121, 122, 126, 127 are impedance components in a double-to-single-ended circuit, which are illustrated as resistors, but the description is not limited thereto, and for example, impedance components implemented by using a switched capacitor technology are also possible;

123, 125 are capacitor devices in a double-to-single-ended circuit.

The above describes a two-to-one circuit architecture of a conventional fully-differential switched-capacitor filter. Because the double-end-to-single-end circuit and the fully differential switched capacitor filter circuit are relatively independent and are realized in a direct cascade mode, the circuit has the following inevitable defects:

1) noise and offset of the double-end-to-single-end circuit directly affect the output voltage. These sources of noise and offset include differential amplifier 124, impedance devices 121, 126, 127, etc.;

2) to compensate for the above-mentioned defect 1), it is necessary to increase the area and power consumption of the differential amplifier 124 and the area of the resistors 121, 127, 122, 126 to reduce the mismatch and noise caused by them. At the same time, layout of the devices in the wafer is also careful to reduce mismatch.

3) The influence of the slew rate of the switched capacitor filter may aggravate the signal nonlinearity of the final single-ended output. The reason is that, as shown in fig. 5, the slew rate causes the output of the switched capacitor filter to have a signal dependent glitch, and the magnitude of the glitch varies with the signal amplitude, and the larger the signal amplitude is, the larger the effect of the glitch on the signal is, which may aggravate the signal nonlinearity.

Based on the above conventional structure, an innovative structure is proposed, which solves the above drawbacks while accomplishing the conventional task.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a single-ended output low-noise fully-differential switched capacitor filter, wherein a double-end-to-single-end circuit is built in a loop of the fully-differential switched capacitor filter, so that the noise and mismatch influence of the double-end-to-single-end circuit and signal nonlinearity brought by slew rate are suppressed.

The technical solution for realizing the purpose of the invention is as follows:

a double-end-to-single-end circuit is arranged in a loop of the fully-differential switched capacitor filter, and an output end of the double-end-to-single-end circuit is connected with a feedback capacitor pair of the fully-differential switched capacitor filter through a switch tube.

Furthermore, a buffer is arranged between the output end of the double-end-to-single-end circuit and the switch tube, and the buffer is composed of a resistor capacitor or an operational amplifier.

Further, the single-ended output low-noise fully-differential switched capacitor filter of the present invention includes: the circuit comprises a signal source, a square wave generator, a fully differential amplifier, a differential amplifier, 1 pair of sampling capacitors, 1 pair of feedback capacitors, 1 pair of integrating capacitors, 6 pairs of switching tubes, 4 resistors and 2 capacitors, wherein the 6 pairs of switching tubes are all connected with the square wave generator; the signal source comprises an input signal source and a direct current bias voltage source, the input signal source and the direct current bias voltage source are sequentially connected, and the other end of the direct current bias voltage source is grounded; one end of the ninth switching tube is connected with an input signal source to obtain an input signal, the other end of the ninth switching tube is connected with one end of the third switching tube and one end of the first sampling capacitor in a common mode, and the other end of the third switching tube is grounded; the other end of the first sampling capacitor is connected with one end of a first switching tube, one end of a seventh switching tube and one end of a first feedback capacitor in a common mode, and the other end of the first switching tube is grounded; the other end of the seventh switch tube and one end of the first integrating capacitor are both connected with the inverting input end of the fully differential amplifier, and the other end of the first integrating capacitor and one end of the first resistor are both connected with the non-inverting output end of the fully differential amplifier; the other end of the first resistor, one end of the second resistor and one end of the first capacitor are all connected with the inverting input end of the differential amplifier, the other end of the second resistor and the other end of the first capacitor are all connected with the output end of the differential amplifier, and the output end of the differential amplifier is used as the output end of the low-noise fully-differential switched capacitor filter with single-ended output; the other end of the first feedback capacitor is connected with one end of an eleventh switching tube and one end of a fifth switching tube in a common mode, and the other end of the fifth switching tube is grounded; the other end of the eleventh switching tube and one end of the sixth switching tube are connected with the output end of the differential amplifier; one end of a tenth switching tube is connected with a direct-current bias voltage source to obtain an input signal, the other end of the tenth switching tube is connected with one end of a fourth switching tube and one end of a second sampling capacitor in a common mode, and the other end of the fourth switching tube is grounded; the other end of the second sampling capacitor is connected with one end of a second switching tube, one end of an eighth switching tube and one end of a second feedback capacitor in common, and the other end of the second switching tube is grounded; the other end of the eighth switching tube and one end of the second integrating capacitor are both connected with the non-inverting input end of the fully differential amplifier, and the other end of the second integrating capacitor and one end of the fourth resistor are both connected with the inverting output end of the fully differential amplifier; the other end of the fourth resistor, one end of the third resistor and one end of the second capacitor are connected with the non-inverting input end of the differential amplifier, and the other end of the third resistor and the other end of the second capacitor are grounded; the other end of the second feedback capacitor is connected with one end of the twelfth switching tube and the other end of the sixth switching tube in a common mode, and the other end of the twelfth switching tube is grounded.

Further, the single-ended output low-noise fully-differential switched capacitor filter of the present invention includes: the circuit comprises a signal source, a square wave generator, a fully differential amplifier, a differential amplifier, 1 pair of sampling capacitors, 1 pair of feedback capacitors, 1 pair of integrating capacitors, 6 pairs of switching tubes, 5 resistors and 3 capacitors, wherein the 6 pairs of switching tubes are all connected with the square wave generator; the signal source comprises an input signal source and a direct current bias voltage source, the input signal source and the direct current bias voltage source are sequentially connected, and the other end of the direct current bias voltage source is grounded; one end of the ninth switching tube is connected with an input signal source to obtain an input signal, the other end of the ninth switching tube is connected with one end of the third switching tube and one end of the first sampling capacitor in a common mode, and the other end of the third switching tube is grounded; the other end of the first sampling capacitor is connected with one end of a first switching tube, one end of a seventh switching tube and one end of a first feedback capacitor in a common mode, and the other end of the first switching tube is grounded; the other end of the seventh switch tube and one end of the first integrating capacitor are both connected with the inverting input end of the fully differential amplifier, and the other end of the first integrating capacitor and one end of the first resistor are both connected with the non-inverting output end of the fully differential amplifier; the other end of the first resistor, one end of the second resistor and one end of the first capacitor are all connected with the inverting input end of the differential amplifier, the other end of the second resistor and the other end of the first capacitor are all connected with the output end of the differential amplifier, and the output end of the differential amplifier is used as the output end of the low-noise fully-differential switched capacitor filter with single-ended output; the other end of the first feedback capacitor is connected with one end of an eleventh switching tube and one end of a fifth switching tube in a common mode, and the other end of the fifth switching tube is grounded; the other end of the eleventh switching tube is connected with one end of a third capacitor, one end of a fifth resistor and one end of a sixth switching tube in a common mode, the other end of the third capacitor is grounded, and the other end of the fifth resistor is connected with the output end of the differential amplifier; one end of a tenth switching tube is connected with a direct-current bias voltage source to obtain an input signal, the other end of the tenth switching tube is connected with one end of a fourth switching tube and one end of a second sampling capacitor in a common mode, and the other end of the fourth switching tube is grounded; the other end of the second sampling capacitor is connected with one end of a second switching tube, one end of an eighth switching tube and one end of a second feedback capacitor in common, and the other end of the second switching tube is grounded; the other end of the eighth switching tube and one end of the second integrating capacitor are both connected with the non-inverting input end of the fully differential amplifier, and the other end of the second integrating capacitor and one end of the fourth resistor are both connected with the inverting output end of the fully differential amplifier; the other end of the fourth resistor, one end of the third resistor and one end of the second capacitor are connected with the non-inverting input end of the differential amplifier, and the other end of the third resistor and the other end of the second capacitor are grounded; the other end of the second feedback capacitor is connected with one end of the twelfth switching tube and the other end of the sixth switching tube in a common mode, and the other end of the twelfth switching tube is grounded.

Furthermore, in the single-ended output low-noise fully-differential switched capacitor filter of the present invention, the first switch tube and the second switch tube are controlled by the first timing sequence, the third switch tube, the fourth switch tube, the fifth switch tube and the sixth switch tube are controlled by the second timing sequence, and the falling edge of the second timing sequence is later than the falling edge of the first timing sequence; the seventh switch tube and the eighth switch tube are controlled by a third time sequence, the ninth switch tube, the fourth switch tube, the eleventh switch tube and the twelfth switch tube are controlled by a fourth time sequence, and the falling edge of the fourth time sequence is later than that of the third time sequence; the first timing sequence, the second timing sequence, the third timing sequence and the fourth timing sequence are not overlapped with each other.

Furthermore, the capacitance value of the feedback capacitor pair of the single-ended output low-noise fully-differential switch capacitor filter is half of the original capacitance value.

Furthermore, the capacitance value of the sampling capacitor pair of the single-ended output low-noise fully-differential switched capacitor filter is twice that of the original sampling capacitor pair.

Compared with the prior art, the invention adopting the technical scheme has the following technical effects:

1. according to the invention, the fault caused by clock switching is eliminated by adding the resistor device and the capacitor device at the output port of the double-end-to-single-end circuit.

2. The invention realizes the purpose of keeping the direct current gain unchanged by reducing the capacitance value of the feedback capacitor pair to 1/2 or doubling the capacitance value of the sampling capacitor pair.

Drawings

Fig. 1 is a schematic diagram of a conventional fully-differential switched capacitor filter from double-ended to single-ended.

Fig. 2 is a schematic diagram of a single-ended low-noise fully-differential switched capacitor filter according to the present invention.

Fig. 3 is a simplified block diagram of a conventional architecture and an inventive architecture, fig. a is a simplified block diagram of a conventional architecture, and fig. B is a simplified block diagram of an inventive architecture.

Fig. 4 is a comparison graph of the effects of the conventional structure and the structure of the present invention, wherein a is a graph of the effects of the conventional structure, and B is a graph of the effects of the structure of the present invention.

Fig. 5 shows the effect of the slew rate on the signal in the conventional structure.

Fig. 6 is a graph of the slope rate versus the frequency spectrum of the conventional structure and the structure of the present invention, in which a is a graph of the output frequency spectrum of the fully-differential switched capacitor filter, B is a graph of the output signal frequency spectrum of the conventional structure, and C is a graph of the output signal frequency spectrum of the structure of the present invention.

The reference numerals have the meanings given below: 101: ninth switching tube, 102: first feedback capacitance, 103: first sampling capacitance, 104: seventh switching tube, 105: eleventh switching tube, 106: fifth switching tube, 107: third switching tube, 108: first switching tube, 109: fourth switching tube, 110: second switching tube, 111: second integrating capacitance, 112: second feedback capacitance, 113: twelfth switching tube, 114: first integrating capacitance, 115: sixth switching tube, 116: second sampling capacitance, 117: eighth switching tube, 118: tenth switching tube, 119: input signal source, 120: dc bias voltage source, 121: first resistance, 122: second resistance, 123: first capacitance, 124: differential amplifier, 125: second capacitance, 126: third resistance, 127: fourth resistance, 128: fully differential amplifier, 129: fifth resistance, 130: and a third capacitor.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.

A double-end-to-single-end circuit is arranged in a loop of the fully-differential switched capacitor filter, an output end of the double-end-to-single-end circuit is connected with a feedback capacitor pair of the fully-differential switched capacitor filter through a switch tube, a buffer is arranged between the output end of the double-end-to-single-end circuit and the switch tube, and the buffer is composed of resistance capacitors or operational amplifiers.

Under the premise of not influencing the normal function, the invention utilizes the loop gain characteristic of the switched capacitor filter to eliminate the influence of noise, mismatch and the like caused by a double-end-to-single-end circuit in the traditional structure shown in figure 1. The detailed mode is as follows:

1) the connection relationship between the switching devices 105 and 113 and the output terminals Vop and Von of the fully differential operational amplifier 128 is disconnected, and the connection relationship between the switching devices 115 and the ground is disconnected.

2) A129 resistor and a 130 capacitor device are added at the output end Vout of the double-end-to-single-end circuit, one end of the resistor 129 is connected with the output Vout, the other end of the resistor 129 is connected with one end of the capacitor 130, for convenience of description, the line connected with the resistor 129 and the capacitor 130 is named Vfb, and the other end of the capacitor 130 is grounded. 129. 130 is primarily aimed at isolating the direct effect of the switching device switching transient on the output Vout. The values can be determined according to actual conditions.

3) In step 1), the end 105 disconnected from Vop is in turn connected to Vfb, and the end 115 disconnected from ground is also in turn connected to Vfb. 113 is disconnected from Von and is in turn connected to ground.

4) In order to ensure that the signal gain of the whole circuit structure is unchanged, the capacitance values of the feedback capacitors 102 and 112 need to be changed to be smaller than 1/2, or the capacitance values of the input capacitors 103 and 116 need to be increased to be 2 times larger than the original capacitance values. The reason for this modification is that the feedback part of the circuit has been switched off from the original fully differential output Vop, Von to the now single-ended output Vout, and if no change is made in the magnitudes of the capacitances 102, 112, or 103, 116, the equivalent feedback amount is directly increased to 2 times the original, which is equivalent to a 1-fold attenuation of the signal gain. Whether the feedback capacitance 102, 112 is reduced or the input capacitance 103, 116 is increased depends on the trade-off of noise performance and speed for the actual circuit.

In this way, only a few changes are needed, and the rest of the structure, including the timing portion, may be kept unchanged, as shown in fig. 3, which is a simplified block diagram comparison of the conventional structure and the structure of the present invention. The purpose of the invention can be achieved: the influence of noise, mismatch and the like of a double-end-to-single-end circuit in the traditional structure (as shown in figure 1) on the circuit performance is reduced; reducing the nonlinear effect of slewrate.

Because only the connection is modified and a small number of devices 129, 130 are added. The invention does not burden the area and power consumption of the chip, on the contrary, because the invention reduces the influence of noise, mismatch and the like of the double-end to single-end circuit, namely under the same performance index, the invention reduces the design area and the power consumption requirement of the double-end to single-end circuit, thereby further reducing the area and the power consumption of the chip.

The improved circuit has the characteristics of wide application range and flexibility, can be applied to a signal acquisition system of a sensor, and can also be applied to a high-precision ADC (analog to digital converter), a DAC (digital to analog converter) and other signal processing circuits of switched capacitors.

For the noise and mismatch effect of the double-to-single-ended circuit, the actual effect comparison can be seen from fig. 4, and 3 sets of comparison tests are respectively performed on the conventional structure and the improved structure: a, the operational amplifier 124 of the double-end-to-single-end circuit has no offset, and the resistors 121 and 127 have no mismatch; b, the operational amplifier 124 of the double-end-to-single-end circuit has offset of 200mV, and the resistors 121 and 127 have no mismatch; c, the operational amplifier 124 of the double-to-single-ended circuit has an offset of 200mV, and the resistors 121 and 127 have a 25% mismatch. It is obvious from the results that the conventional structure is sensitive to the offset of the operational amplifier 124 and the mismatch of the resistors 121 and 127, and the output result changes dramatically; the improved structure is not sensitive to the offset of the operational amplifier 124 and the mismatch of the resistors 121 and 127 under the same comparison condition, and has no obvious change.

From the comparison experiment results, the improved structure of the invention can obviously improve the defects of the traditional structure.

The signal non-linearity for the slew rate will also be suppressed by the loop. As shown in fig. 6, the comparison of the output signal spectra of the conventional and improved structures is shown. It can be clearly seen that the improved structure can suppress the offset voltage which changes with the signal amplitude.