CN210469230U - Pre-amplification circuit for high-output impedance sensor - Google Patents
Pre-amplification circuit for high-output impedance sensor Download PDFInfo
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- CN210469230U CN210469230U CN201922049800.3U CN201922049800U CN210469230U CN 210469230 U CN210469230 U CN 210469230U CN 201922049800 U CN201922049800 U CN 201922049800U CN 210469230 U CN210469230 U CN 210469230U
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- 238000003199 nucleic acid amplification method Methods 0.000 title claims description 12
- 230000005669 field effect Effects 0.000 claims abstract description 43
- 230000009467 reduction Effects 0.000 claims abstract description 39
- 239000003990 capacitor Substances 0.000 claims abstract description 15
- 230000008878 coupling Effects 0.000 claims abstract description 9
- 238000010168 coupling process Methods 0.000 claims abstract description 9
- 238000005859 coupling reaction Methods 0.000 claims abstract description 9
- 230000003321 amplification Effects 0.000 claims description 10
- 238000006386 neutralization reaction Methods 0.000 claims description 5
- 239000002184 metal Substances 0.000 claims description 4
- 230000003472 neutralizing effect Effects 0.000 claims description 4
- 230000008901 benefit Effects 0.000 abstract description 3
- 230000002238 attenuated effect Effects 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 230000010355 oscillation Effects 0.000 description 2
- 230000004075 alteration Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
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Abstract
The utility model provides a preamplification circuit for high output impedance sensor, including signal input port, signal output port, resistance R1, resistance R2, noise reduction resistance R3, resistance R4, coupling capacitance C2, field effect transistor T1, noise reduction unit and DC power supply; the signal input port is electrically connected with the grid of the field effect transistor T1 through a coupling capacitor C2; the resistor R1 is connected with the resistor R2 in series, one end of the resistor R1 after the resistor R2 is connected with the direct current power supply in series is electrically connected, the other end of the resistor R1 after the resistor R2 is connected with the direct current power supply in series is grounded, and the common end of the resistor R3 is electrically connected with the input end of the noise reduction unit; the output end of the noise reduction unit is electrically connected with the grid electrode of a field effect transistor T1, and the drain electrode of the field effect transistor T1 is electrically connected with the direct current power supply; the source electrode of the field effect transistor T1 is electrically connected with the signal output port and is grounded through a resistor R4. The utility model has the advantages of reduce the circuit background noise, reduced the requirement of selecting to resistance device noise characteristic.
Description
Technical Field
The utility model belongs to the technical field of amplifier circuit, concretely relates to preamplification circuit for high output impedance sensor.
Background
The existing capacitive reactance characteristic sensors all have very high output impedance (sometimes as high as about 1 giga ohm), in order to ensure that the sensor signal can be effectively output to a signal amplification system, a preamplifier is generally required to be connected to the output end of the sensor, and the preamplifier is required to have the characteristics of high input impedance, low output impedance and low noise, so that the sensor signal is ensured not to be attenuated, and the signal output has a sufficiently high signal-to-noise ratio. In any sensor measurement system, a key factor in determining the signal-to-noise ratio of the system is the signal-to-noise ratio of the sensor signal output. For a high output impedance type sensor, it is necessary to configure a suitable preamplifier circuit to ensure effective output without signal attenuation, but the signal-to-noise ratio of the sensor output is also reduced due to noise of electronic components in the preamplifier circuit, so the design of the preamplifier needs to satisfy the transformation relationship of high input impedance and low output impedance, and how to effectively control the background noise of the preamplifier circuit is also important to consider.
The preamplifier circuit used in the high output impedance sensor product at present usually adopts the source follower circuit composed of the junction field effect tube, the circuit structure is simple, and is suitable for the sensor, the performance advantage of the junction field effect tube is fully utilized, and the preamplifier circuit has the characteristics of high input impedance, low output impedance and low noise. The background noise of the preamplifier is controlled and reduced by adopting the technology, and the defects are that the performance of the background noise is completely influenced and restricted by the noise characteristics of components in the circuit, so that the requirements on the noise quality of main components are high, and the manufacturing cost of the circuit is increased; if the background noise of the circuit needs to be further reduced and the signal-to-noise ratio of the sensor for measuring the weak signal needs to be improved, the noise quality of main components needs to be further improved, and the manufacturing cost of the circuit is greatly increased.
SUMMERY OF THE UTILITY MODEL
The utility model discloses to above not enough, provide a reduce circuit background noise, improve output signal SNR, reduced to resistance device noise characteristic selection requirement be used for high output impedance sensor's preamplification circuit.
In order to achieve the above object, the utility model provides a following technical scheme: a pre-amplification circuit for a high-output impedance sensor comprises a signal input port, a signal output port, a resistor R1, a resistor R2, a noise reduction resistor R3, a resistor R4, a coupling capacitor C2, a field effect transistor T1, a noise reduction unit and a direct-current power supply; the signal input port is electrically connected with the grid of the field effect transistor T1 through a coupling capacitor C2; the resistor R1 is connected in series with the resistor R2, one end of the resistor R1 and the resistor R2 which are connected in series is electrically connected with the direct-current power supply, the other end of the resistor R1 and the resistor R2 which are connected in series is grounded, and the common end of the resistor R1 and the resistor R2 which are connected in series is electrically connected with the input end of the noise reduction unit through the noise reduction resistor R3; the output end of the noise reduction unit is electrically connected with the grid electrode of a field effect transistor T1, and the drain electrode of the field effect transistor T1 is electrically connected with the direct current power supply; the source electrode of the field effect transistor T1 is electrically connected with the signal output port and is grounded through a resistor R4.
Preferably, the noise reduction unit includes a diode D1, a diode D2; the diode D1 and the diode D2 are connected in anti-parallel.
Preferably, the type of the diode D1 and the type of the diode D2 are both 1N 4148.
Preferably, the device also comprises a neutralization unit; the neutralizing unit comprises a capacitor C1; one end of the capacitor C1 is connected with the direct current power supply, and the other end of the capacitor C1 is electrically connected with the input end of the noise reduction unit.
Preferably, the field effect transistor T1 is an N-channel junction field effect transistor.
Preferably, the resistor R1, the resistor R2, and the noise reduction resistor R3 are all metal film resistors or wire-wound resistors.
Has the advantages that:
1. the utility model discloses an add between field effect transistor T1's grid and the resistance R3 of making an uproar of falling and fall the unit of making an uproar, block resistance R1, resistance R2, fall the grid that resistance R3 produced the thermal noise and get into field effect transistor T1 of making an uproar, the influence to input signal has been reduced to reduce the background noise of circuit, improve the output signal SNR, further reduced and selected the requirement to resistance device noise characteristic, reduced the manufacturing cost of circuit.
2. The utility model discloses a field effect transistor T1's drain electrode and the input of the unit of making an uproar of falling add the neutralization unit, have attenuated the self-excited oscillation that produces between field effect transistor T1's the drain electrode and the grid to output signal's influence to reduce the background noise of circuit, improve output signal SNR.
Drawings
Fig. 1 is a schematic circuit diagram of the present invention.
In the figure: 1. a signal input port; 2. a signal output port; 3. a noise reduction unit; 4. a neutralization unit; 5. a direct current power supply.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.
The utility model discloses the technical scheme of well each embodiment can make up, and technical feature in the embodiment does to make up and forms new technical scheme.
Referring to fig. 1, the present invention provides the following technical solutions: a pre-amplification circuit for a high-output impedance sensor comprises a signal input port 1, a signal output port 2, a resistor R1, a resistor R2, a noise reduction resistor R3, a resistor R4, a coupling capacitor C2, a field effect transistor T1, a noise reduction unit 3 and a direct-current power supply 5; the signal input port 1 is electrically connected with the gate of the field effect transistor T1 through a coupling capacitor C2; the resistor R1 is connected in series with the resistor R2, one end of the resistor R1 and the resistor R2 which are connected in series is electrically connected with the direct current power supply 5, the other end of the resistor R1 and the resistor R2 which are connected in series is grounded, and the common end of the resistor R1 and the resistor R2 which are connected in series is electrically connected with the input end of the noise reduction unit (3) through the noise reduction resistor R3; the output end of the noise reduction unit 3 is electrically connected with the gate of a field effect transistor T1, and the drain of the field effect transistor T1 is electrically connected with the direct current power supply 5; the source of the fet T1 is electrically connected to the signal output port 2 and is grounded via a resistor R4.
The noise reduction unit 3 comprises a diode D1, a diode D2; the diode D1 and the diode D2 are connected in anti-parallel. The thermal noise generated by the resistor R1, the resistor R2 and the noise reduction resistor R3 is smaller than the turn-on voltage of the diode D1 or the diode D2, so that the thermal noise generated by the resistor R1, the resistor R2 and the noise reduction resistor R3 can be effectively prevented from entering the gate of the field-effect transistor T1, and the influence of the thermal noise on the input signal of the gate terminal of the field-effect transistor T1 is effectively reduced. The dc bias voltage formed by the dc power supply 5 via the resistor 1, the resistor R2, and the noise reduction resistor R3 is much larger than the on-state voltage of the diode D1 or the diode D2, and can normally supply the dc bias voltage to the gate of the fet T1 without affecting the amplification effect of the fet T1 on the input signal.
The types of the diode D1 and the diode D2 are both 1N 4148. The thermal noise generated by the resistor can be effectively blocked.
Also comprises a neutralization unit 4; the neutralizing unit 4 includes a capacitance C1; one end of the capacitor C1 is connected to the dc power supply 5, and the other end is electrically connected to the input end of the noise reduction unit 3. The capacitor C1 attenuates the effect of the self-oscillation generated between the drain and the gate of the fet T1 on the output signal.
The field effect transistor T1 is an N-channel junction field effect transistor. The characteristics of high input impedance, low output impedance and low noise can be effectively realized.
The resistor R1, the resistor R2 and the noise reduction resistor R3 are all metal film resistors or wire-wound resistors. The resistor R1, the resistor R2, and the noise reduction resistor R3 are preferably low noise resistors such as a metal film resistor and a wire winding resistor. The background noise of the circuit can be effectively reduced.
Example 1:
the utility model discloses a theory of operation:
an input signal enters a grid electrode of a field effect transistor T1 through a signal input port through a coupling capacitor C3, a direct current power supply 5 is connected to a drain electrode of the field effect transistor T1, and after voltage division is carried out through a resistor R1 and a resistor R2, direct current bias voltage is provided for the grid electrode of the field effect transistor T1 through a noise reduction resistor R3 and a noise reduction unit 3 in sequence, thermal noise generated by the resistor R1, the resistor R2 and the noise reduction resistor R3 is blocked by the noise reduction unit 3, the influence of the resistance thermal noise on a grid end input signal of the field effect transistor T1 is reduced, the background noise of the circuit is reduced, and the noise characteristic selection requirement of a resistance device is further reduced; an input signal of the grid end of the field effect transistor T1 is amplified by the field effect transistor T1 and then is output to the signal output end from the source electrode of the field effect transistor T1;
by adding the neutralizing unit 4 between the drain of the field effect transistor T1 and the input end of the noise reduction unit 3, the self-excited oscillation generated between the drain and the grid of the field effect transistor T1 is attenuated, so that the influence of the field effect transistor T1 on the amplification of the input signal is reduced, the input signal can be effectively amplified, the background noise of the circuit is reduced, and the signal-to-noise ratio of the output signal of the signal output port 2 is improved.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (6)
1. A preamplifier circuit for a high output impedance sensor, characterized by: the noise reduction circuit comprises a signal input port (1), a signal output port (2), a resistor R1, a resistor R2, a noise reduction resistor R3, a resistor R4, a coupling capacitor C2, a field effect transistor T1, a noise reduction unit (3) and a direct current power supply (5); the signal input port (1) is electrically connected with the gate of the field effect transistor T1 through a coupling capacitor C2; the resistor R1 is connected with the resistor R2 in series, one end of the resistor R1 and the resistor R2 which are connected in series is electrically connected with the direct current power supply (5), the other end of the resistor R1 and the resistor R2 which are connected in series is grounded, and the common end of the resistor R1 and the resistor R2 which are connected in series is electrically connected with the input end of the noise reduction unit (3) through the noise reduction resistor R3; the output end of the noise reduction unit (3) is electrically connected with the grid of a field effect transistor T1, and the drain of the field effect transistor T1 is electrically connected with the direct current power supply (5); the source electrode of the field effect transistor T1 is electrically connected with the signal output port (2) and is grounded through a resistor R4.
2. The pre-amplification circuit for a high output impedance sensor of claim 1, wherein: the noise reduction unit (3) comprises a diode D1, a diode D2; the diode D1 and the diode D2 are connected in anti-parallel.
3. The pre-amplification circuit for a high output impedance sensor of claim 2, wherein: the types of the diode D1 and the diode D2 are both 1N 4148.
4. The pre-amplification circuit for a high output impedance sensor of claim 2, wherein: also comprises a neutralization unit (4); the neutralizing unit (4) comprises a capacitance C1; one end of the capacitor C1 is connected with the direct current power supply (5), and the other end of the capacitor C1 is electrically connected with the input end of the noise reduction unit (3).
5. The pre-amplification circuit for a high output impedance sensor of claim 4, wherein: the field effect transistor T1 is an N-channel junction field effect transistor.
6. The pre-amplification circuit for a high output impedance sensor of claim 5, wherein: the resistor R1, the resistor R2 and the noise reduction resistor R3 are all metal film resistors or wire-wound resistors.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201922049800.3U CN210469230U (en) | 2019-11-25 | 2019-11-25 | Pre-amplification circuit for high-output impedance sensor |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201922049800.3U CN210469230U (en) | 2019-11-25 | 2019-11-25 | Pre-amplification circuit for high-output impedance sensor |
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| CN210469230U true CN210469230U (en) | 2020-05-05 |
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| CN201922049800.3U Active CN210469230U (en) | 2019-11-25 | 2019-11-25 | Pre-amplification circuit for high-output impedance sensor |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112290899A (en) * | 2020-10-26 | 2021-01-29 | 杭州爱华仪器有限公司 | Measuring circuit preamplifier |
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2019
- 2019-11-25 CN CN201922049800.3U patent/CN210469230U/en active Active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112290899A (en) * | 2020-10-26 | 2021-01-29 | 杭州爱华仪器有限公司 | Measuring circuit preamplifier |
| CN112290899B (en) * | 2020-10-26 | 2024-02-06 | 杭州爱华仪器有限公司 | Preamplifier of measuring circuit |
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Effective date of registration: 20240327 Address after: Room 601, Building 7, Zone C, Jindao Park, No. 179 Huizhi Middle Road, High tech Development Zone, Changsha City, Hunan Province, 410205 Patentee after: Hunan saineng Environmental Measurement Technology Co.,Ltd. Country or region after: China Address before: 410000 Room 201, building 7, Zone C, jindaoyuan, No. 179, Huizhi Middle Road, high tech Development Zone, Yuelu District, Changsha City, Hunan Province Patentee before: HUNAN SAINENG ENVIRONMENTAL PROTECTION TECHNOLOGY Co.,Ltd. Country or region before: China |