A low leakage current gating switch circuit for high-precision measurement of multi-channel resistors
By using a low-lead current gate switch circuit composed of diodes, transistors and MOS tubes in the multi-track switch circuit, and using an operational amplifier to form a voltage feedback circuit, the problem of large leakage current in multiple-track resistance measurement is solved, and high-precision resistance measurement is achieved.
Patent Information
- Application Number
- CN202111541519.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-12-16
- Publication Date
- 2025-08-01
- Estimated Expiration
- 2041-12-16
AI Technical Summary
The existing multi-gate switch circuit has a problem of large leakage current, resulting in inaccurate resistance measurement.
A low leakage current gate switch circuit composed of diode, transistor and MOS tube is used to form a voltage feedback circuit through an operational amplifier, which converts the leakage current of the MOS tube into the leakage current of the diode, and reduces the reverse voltage on the diode, reducing the overall leakage current.
It significantly reduces leakage current and improves the accuracy of resistance measurement. The leakage current of the MOS tube is reduced to the nanoamp level and the leakage current of the diode is reduced to the pico-amp level, which is suitable for high-precision resistance measurement.
Smart Images
Figure CN114172501B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of circuit design, and particularly relates to a low-leakage current gating switch circuit for high-precision measurement of multiple resistors. Background Art
[0002] Measuring resistors is a very common requirement. For measuring a resistor, the basic method is to inject a standard current I into the resistor, and then measure the voltage V across the resistor. Then the resistance value is V / I. For a multi-channel acquisition system that needs to measure multiple resistors, it is necessary to measure each resistor in turn. The basic switching logic is as Figure 1 , to measure which resistor, close the corresponding two switches and open the other switches. Here, it is necessary to ensure that the switch does not introduce leakage current so as not to affect the measurement result. Using a relay to implement the switch will not introduce leakage current, but the relay is large in size, high in power consumption, and slow in switching action, so it is generally not used. Instead, two MOS transistors are usually used to form a gate switch, Figure 2 which is a conventional gating structure composed of MOS. When it is necessary to measure R1, turn on Q3 and Q4 and turn off Q1 and Q2. However, MOS transistors all have leakage current, so part of the standard current will leak through MOS transistors Q1 and Q2; turn on Q5 and Q6 and turn off Q7 and Q8. Similarly, MOS transistors Q7 and Q8 also have leakage current, and its order of magnitude is in the nanoampere level. Moreover, the leakage current in these two places is determined by the production process of the MOS transistor and is related to temperature, source and drain voltages, and cannot be eliminated by simple data processing methods. In addition, as the number of gating gates increases, the leakage current also becomes larger.
[0003] Therefore, the multi-channel gating switch circuit in the prior art often has problems of large leakage current and inaccurate measurement. Summary of the Invention
[0004] To meet the actual requirements of the resistor measurement circuit, the present invention overcomes the deficiencies of the prior art. The technical problem to be solved is: to provide a low-leakage current gating switch circuit for high-precision measurement of multiple resistors to reduce the leakage current in the circuit and improve the measurement accuracy.
[0005] To solve the above technical problem, the technical solution adopted by the present invention is: a low-leakage current gating switch circuit for high-precision measurement of multiple resistors, including: diodes D1 to D7, transistor Q3, MOS transistors Q1, Q4, Q5, Q6, operational amplifiers U1 and U2;
[0006] The standard current input terminal is connected to the anode of diode D1. The cathode of diode D1 is connected to the drain of MOS transistor Q1. The source of MOS transistor Q1 is connected to the anode of diode D3. The gate of MOS transistor Q1 is connected to the injection current gating signal. The cathode of diode D3 is grounded through the resistor under test R4, and the cathode of diode D3 is also connected to the drain of MOS transistor Q5. The source of MOS transistor Q5 is connected to the source of MOS transistor Q4. The drain of MOS transistor Q4 is connected to the source of MOS transistor Q6. The drain of MOS transistor Q6 is connected to the ADC sampling terminal. The gates of MOS transistors Q4, Q5, and Q6 are connected to the ADC sampling gating signal.
[0007] The positive terminal of the operational amplifier U2 is connected to the standard current input terminal, the negative terminal is connected to the output terminal, and the negative terminal is also connected to the cathode of diode D7. The anode of diode D7 is connected to the cathode of diode D2 through the current-limiting resistor R2. The cathode of diode D2 is connected to the cathode of diode D1. The anode of diode D7 is also connected to the collector of transistor Q3. The collector of transistor Q3 is connected to the power supply VEE through the current-limiting resistor R1. The base is connected to the injection current gating signal through the current-limiting resistor R3, and the emitter is grounded.
[0008] The positive terminal of the operational amplifier U1 is connected to the ADC sampling terminal, the negative terminal is connected to the output terminal, the output terminal is connected to the anode of diode D6, the cathode of diode D6 is connected to the anode of diode D2, and the output terminal of the operational amplifier U1 is also connected to the anode of diode D4 through the current-limiting resistor R5. The cathode of diode D4 is connected to the source of MOS transistor Q6.
[0009] The diodes D1, D2, and D7 are switching diodes.
[0010] The diodes D3, D4, and D6 are germanium diodes.
[0011] In addition, the present invention also provides a multi-channel resistor high-precision measurement circuit, including a plurality of the above-mentioned gating switch circuits.
[0012] The above-mentioned gating switch circuits share the operational amplifiers U1 and U2.
[0013] The present invention has the following beneficial effects compared with the prior art:
[0014] 1. In summary, the present invention provides a low-leakage current gating switch circuit for high-precision measurement of multi-channel resistors. By converting the leakage current of the MOS transistor into the leakage current of the diode, and additionally through a simple voltage feedback circuit, the reverse voltage applied to the diode is reduced, enabling the leakage current of the diode to reach the picoampere level, while the leakage current of the MOS transistor is basically in the nanoampere level. Therefore, the leakage current of this circuit can be reduced by thousands of times, having extremely high application value. Additionally, at the ADC sampling end, a voltage feedback circuit is also adopted to reduce the voltage of the MOS transistor to below 0.1 volts, greatly reducing the leakage current of this part of the circuit. Through the combined action of the above circuits, the overall leakage current of the gating switch circuit is extremely low and can be used for high-precision resistor measurement;
[0015] 2. In the present invention, multiple gating gates can be used in parallel to form a multi-channel resistor high-precision measurement circuit, which has low cost, high reliability, and wide implementability. Description of the Drawings
[0016] Figure 1 is a schematic diagram of switch switching for resistor multi-channel sampling in the prior art;
[0017] Figure 2 is a schematic diagram of the structure of a gating gate composed of conventional MOS transistors in the prior art;
[0018] Figure 3 is a circuit schematic diagram of a low-leakage current multi-channel gating switch circuit for high-precision resistor measurement provided by an embodiment of the present invention;
[0019] Figure 4 is a circuit schematic diagram of a multi-channel resistor high-precision measurement circuit provided by Embodiment 2 of the present invention.
[0020] Detailed Embodiment Modes
[0021] To make the technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments and the accompanying drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention; all other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts fall within the scope of protection of the present invention.
[0022] Embodiment 1
[0023] As Figure 3 shown, Embodiment 1 of the present invention provides a low-leakage current gating switch circuit for high-precision measurement of multi-channel resistors, including: diodes D1 to D7, transistor Q3, MOS transistors Q1, Q6, operational amplifiers U1, U2.
[0024] Among them, the standard current input terminal is connected to the anode of diode D1. The cathode of diode D1 is connected to the drain of MOS transistor Q1. The source of MOS transistor Q1 is connected to the anode of diode D3. The gate of MOS transistor Q1 is connected to the injection current gating signal. The cathode of diode D3 is grounded through the resistor under test R4, and the cathode of diode D3 is also connected to the drain of MOS transistor Q5. The source of MOS transistor Q5 is connected to the source of MOS transistor Q4. The drain of MOS transistor Q4 is connected to the source of MOS transistor Q6. The drain of MOS transistor Q6 is connected to the ADC sampling terminal. The gates of MOS transistors Q4, Q5, and Q6 are connected to the ADC sampling gating signal.
[0025] Specifically, the positive terminal of the operational amplifier U2 is connected to the standard current input terminal, the negative terminal is connected to the output terminal, and the negative terminal is also connected to the cathode of diode D7. The anode of diode D7 is connected to the cathode of diode D2 through the current limiting resistor R2. The cathode of diode D2 is connected to the cathode of diode D1. The anode of diode D7 is also connected to the collector of triode Q3. The collector of triode Q3 is connected to the power supply VEE through the current limiting resistor R1. The base is connected to the injection current gating signal through the current limiting resistor R3, and the emitter is grounded.
[0026] Specifically, the positive terminal of the operational amplifier U1 is connected to the ADC sampling terminal, the negative terminal is connected to the output terminal, the output terminal is connected to the anode of diode D6, the cathode of diode D6 is connected to the anode of diode D2, and the output terminal of the operational amplifier U1 is also connected to the anode of diode D4 through the current limiting resistor R5. The cathode of diode D4 is connected to the source of MOS transistor Q6.
[0027] Specifically, in this embodiment, MOS transistors Q4 and Q5 form a standard MOS bidirectional gating circuit. The cathode of diode D3 is connected to the source of MOS transistor Q6 through MOS transistor Q5 and MOS transistor Q4 in sequence. The gates of MOS transistors Q4 and Q5 are connected to the collector of triode Q7. And the drain of MOS transistor Q5 is connected to the cathode of diode D3, the source is connected to the source of MOS transistor Q4. The drain of MOS transistor Q4 is connected to the source of MOS transistor Q6.
[0028] In this embodiment, on the basis of the bidirectional gating circuit composed of conventional MOS gates, a MOS gate Q6 is added, and the voltage at the ADC sampling terminal will be buffered by an operational amplifier and fed back to the source of Q6. The current injection gating circuit is composed of low leakage current diodes and MOS transistors to form the gating circuit, and the voltage signals at the standard current injection terminal and the ADC sampling terminal will be buffered by their respective operational amplifiers and fed back to this gating circuit.
[0029] A low-leakage current gating switch circuit for high-precision measurement of multiple resistors provided by an embodiment of the present invention converts the leakage current of an MOS transistor into the leakage current of a diode, and reduces the voltage on the diode and the MOS through a feedback circuit, further reducing the overall leakage current, which meets the requirements of high-precision resistor measurement. Operational amplifiers U1 and U2 form two voltage follower circuits to buffer the two voltages, namely the voltage v1 of the standard current input and the voltage v2 output by the ADC sampling terminal, and then connect the two buffered voltages back to the gating switch circuit to reduce the voltage difference across the diode and the MOS transistor in the circuit, further reducing the leakage current.
[0030] The working principle of the embodiment of the present invention is as follows:
[0031] Assume that the forward conduction voltage drops of the diodes D1, D2, and D7 in the circuit are vd, the forward conduction voltage drops of the diodes D3, D4, and D6 are vdm, and the voltage drop of the conducting MOS transistor is negligible.
[0032] 1. When the current injection is selected, the injection current gating signal is high level, then the MOS transistor Q1 conducts, and the standard current I is injected into the current-limiting resistor R4. The triode Q3 conducts, then the voltage at the right end of the current-limiting resistor R2 is pulled to 0, the diode D6 conducts, and the voltage v2 at the ADC sampling terminal is buffered by the operational amplifier U1 and then clamps the voltage at the right end of the diode D2 to v2 - vdm through the diode D6; the diode D3 conducts, and the voltage at the upper end of the diode D3 is v2 + vdm, then the voltage at the left end of the diode D2 is v2 + vdm. It can be seen that the reverse voltage difference across the diode D2 is 2 * vdm. By selecting a diode with a low forward conduction voltage drop, the reverse voltage difference on D2 can be controlled to be less than 0.1 V, and D2 is a low-leakage current diode, so the generated leakage current is extremely small. At this time, no leakage current flows into or out of the ADC sampling terminal.
[0033] 2. When the current injection is not selected, the injection current gating signal is low level, then the MOS transistor Q1 is cut off, the triode Q3 is cut off, and the voltage v1 at the standard current I injection terminal is buffered by the operational amplifier U2 and clamps the voltage at the right end of the current-limiting resistor R2 to v1 + vd. The voltage across the current-limiting resistor R2 is negligible, then the voltage at the left end of the diode D2 is v1, and the reverse voltage difference across the diode D1 is almost 0, and the generated leakage current is negligible. The corresponding ADC sampling gating signal is high, then the source voltage of the MOS transistor Q6 is v2 - vdm, and the drain voltage is v2, which is equivalent to the voltage difference between the source and the gate of the MOS transistor Q6 being vdm. By selecting a diode with a low forward conduction voltage drop, this voltage difference can be less than 0.1 V, and the leakage current can be ignored.
[0034] Specifically, in this embodiment, diodes D3, D4, and D6 are selected as diodes with low forward voltage drop, such as germanium diodes, which can reduce the voltage difference to less than 0.1 volts; diodes D1, D2, and D7 are selected as diodes with low reverse leakage current, such as switching diodes like BAV99, which can greatly reduce the overall leakage current of the circuit.
[0035] In this embodiment, if there is no operational amplifier U1 to buffer the voltage v2 and feedback it to the source of MOS transistor Q6 through diode D4, the source and drain voltages of MOS transistor Q6 will be approximately v2, which is much greater than 0.1 volts, resulting in a large leakage current. If there is no operational amplifier U1 to buffer the voltage and feedback it to the right end of diode D2 through diode D6, the voltage at the right end of diode D2 is 0, and the voltage at the left end is v1 - vd, resulting in an unstable and potentially large reverse voltage across diode D2, and the resulting leakage current is larger than that of this solution; if there is no operational amplifier U2 to buffer the voltage v1 and clamp the voltage at the right end of diode D2 to v1 + vd through diode D7, the voltage at the right end of diode D2 is VEE, and the voltage at the left end is VEE - vd, resulting in a reverse voltage across diode D1 of VEE - vd - v1, which is unstable and potentially large, and the resulting leakage current is larger than that of this solution. Therefore, by setting up the voltage feedback circuit, the reverse voltage across the diode is reduced, that is, the reverse leakage current of the diode is reduced. And the reverse voltage across the diode is fixed, which is beneficial for further compensating this leakage current.
[0036] Embodiment 2
[0037] As Figure 4 shown, Embodiment 2 of the present invention provides a multi-channel resistor high-precision measurement circuit, which includes two gating switch circuits as described in Embodiment 1. Specifically, in this embodiment, the various gating switch circuits share operational amplifiers U1 and U2.
[0038] In this embodiment, by controlling the levels of the injection current gating terminal and the ADC sampling gating terminal in each gating switch circuit, one of the switch circuits can be gated to perform resistor measurement, with low leakage current and high measurement accuracy.
[0039] Figure 4 Only the structural schematic diagram of the multi-channel resistor high-precision measurement circuit including 2-channel gating switch circuits is given. It should be noted that the multi-channel resistor high-precision measurement circuit of Embodiment 2 of the present invention is not limited to including 2-channel gating switch circuits, and can include more, such as 3 to 10 channels, so as to realize the measurement of multi-channel resistors.
[0040] In summary, the present invention provides a low-leakage current gating switch circuit for high-precision measurement of multiple resistors. By converting the leakage current of the MOS transistor into the leakage current of a diode, and additionally through a simple voltage feedback circuit, the reverse voltage applied to the diode is reduced, enabling the leakage current of the diode to reach the picoampere level, while the leakage current of the MOS transistor is basically in the nanoampere level. Therefore, the leakage current of this circuit can be reduced by thousands of times, having extremely high application value. Additionally, at the ADC sampling end, a voltage feedback circuit is also adopted to reduce the voltage of the MOS transistor to below 0.1 volts, greatly reducing the leakage current of this part of the circuit.
[0041] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A low-leakage current gating switch circuit for high-precision measurement of multi-channel resistors, characterized in that, Comprising: Diodes D1 to D7, transistor Q3, MOS transistors Q1, Q4, Q5, Q6, operational amplifiers U1, U2; The standard current input terminal is connected to the anode of diode D1. The cathode of diode D1 is connected to the drain of MOS transistor Q1. The source of MOS transistor Q1 is connected to the anode of diode D3. The gate of MOS transistor Q1 is connected to the injection current gating signal. The cathode of diode D3 is grounded through the resistance to be measured R4, and the cathode of diode D3 is also connected to the drain of MOS transistor Q5. The source of MOS transistor Q5 is connected to the source of MOS transistor Q4. The drain of MOS transistor Q4 is connected to the source of MOS transistor Q6. The drain of MOS transistor Q6 is connected to the ADC sampling terminal. The gates of MOS transistors Q4, Q5, Q6 are connected to the ADC sampling gating signal. The positive terminal of the operational amplifier U2 is connected to the standard current input terminal, the negative terminal is connected to the output terminal, and the negative terminal is also connected to the cathode of diode D7. The anode of diode D7 is connected to the cathode of diode D2 through the current-limiting resistor R2. The cathode of diode D2 is connected to the cathode of diode D1. The anode of diode D7 is also connected to the collector of transistor Q3. The collector of transistor Q3 is connected to the power supply VEE through the current-limiting resistor R1. The base is connected to the injection current gating signal through the current-limiting resistor R3, and the emitter is grounded. The positive terminal of the operational amplifier U1 is connected to the ADC sampling terminal, the negative terminal is connected to the output terminal, the output terminal is connected to the anode of diode D6, the cathode of diode D6 is connected to the anode of diode D2, and the output terminal of the operational amplifier U1 is also connected to the anode of diode D4 through the current-limiting resistor R5. The cathode of diode D4 is connected to the source of MOS transistor Q6.
2. The low-leakage current gating switch circuit for high-precision measurement of multiple resistors according to claim 1, wherein The diodes D1, D2, D7 are switch diodes.
3. The low-leakage current gating switch circuit for high-precision measurement of multiple resistors according to claim 1, characterized in that, The diodes D3, D4, D6 are germanium diodes.
4. A multi-channel resistor high-precision measurement circuit, characterized in that, Comprising a plurality of gating switch circuits as described in any one of claims 1 to 3.
5. The high-precision measurement circuit for multiple resistors according to claim 4, characterized in that, The respective gating switch circuits share the operational amplifiers U1, U2.
Citation Information
Patent Citations
Signal acquisition device, signal acquisition method, display device and electronic equipment
CN110929645A
Current sensing circuit
JP2018179571A