Low-noise accurate amplifying circuit and its performance improvement method based on operational amplifierTechnical field
The present invention relates to Analogical Electronics technical fields, are based particularly on the low-noise accurate amplification electricity of operational amplifierThe performance improvement method on road.
Background technique
Integrated operational amplifier amplifier in modern computer Circuit Aided Design and is imitated within time the past few decadesDevelopment at full speed very and under the overall background of the continuous development of manufacture of semiconductor technique and material technology is obtained.It is corresponding to be based on collectionAlso there is significant progress in terms of noise, distortion performance at the low noise amplifier circuit of operational amplifier.And with its circuitPeripheral circuit is succinct, and circuit building method freedom and flexibility, functional circuit debugging cycle is short, the optional wide scope of device, between deviceConsistency it is relatively high, relative separation device circuitry possesses higher stability and cheap etc. glamour, meshBefore have become measuring instrument signal put and amplify in advance, professional audio it is preposition amplification with all other low frequencies, ultrasound or evenThe preferred implementation of 1GHz degree frequency signal amplification.But with the miniature promotion of manufacture of semiconductor, operational amplifier deviceInternal conductor, semiconductor, bottom liner and dopant material various noise effects also constantly highlighting, and formd significantRestriction contradiction.In the high-performance that the nineties in last century AD797, LT1028 are representative, low noise low distortion precision operation amplifierAfter device device issues volume production, the research and development of new product of higher performance operational amplifier and listing are promoted in world wide, start to exposeApparent declining trend out.
Therefore, the simple amplifying circuit by using the example in electronic circuit textbook, by the way that higher property is replacedThe novel operational amplifier of energy has become day to promote the realization set pattern of circuit noise, total harmonic distortion plus noise (THD+N)Benefit is difficult.At the same time, the high code rate professional audio recording such as 32bit 768kHz, 22.4MHz DSD and playback, precision analog electricityThe emerging forward position application such as signal measurement and instrument calibration, biological weak electric signal perception and gravitational wave detection, seismic wave detection is ledAccurate low-frequency analog signal including domain and sonar detection, ultrasonic imaging, supersonic sounding amplifies scene, all to amplifying circuitNoise, total harmonic distortion plus noise (THD+N) performance propose more stringent requirement.
Circuit noise and total distortion performance are promoted by circuitry means, early has become the major well-known electronic equipment production in the worldThe customary means of the promotion product competitiveness of quotient.The analog recording amplifier section of SONY profession master tape sound pick-up outfit PCM3348HR,It has used and circuit is promoted based on op-amp noise, distortion performance.Its principle is to carry out the single channel input resistance of input signalAnti- matching and Hyblid Buffer Amplifier, but the circuit is insufficient in overall noise, distortion performance, is not able to satisfy modern 32bitThe voice applications of the high code rate such as 768kHz, 22.4MHz DSD.Used in MBL audio preamplifier MBL6010D based onThe amplifying circuit of high performance operational amplifier, principle are that the buffering impedance matching of input signal is carried out using operational amplifier,And divide overall gain and adjustable gain by way of multistage amplification and multistage potentiometer, and largely use AD797 high-performanceOperational amplifier and metal thin film resistor.But because its single channel amplifying circuit is by the limit of single operational amplifier linear power rangeSystem, for the linear working state for keeping operational amplifier, the resistance and potentiometer numerical value on signal path are still higher.It comes fromThe influence of noise of these Primary Components noise of circuit entirety, total harmonic distortion plus noise (THD+N) performance further mentionIt rises.HP/Agilent has been used in the measurement input path of 34401A, 3458A precision multimeter based on operational amplifierHigh performance circuit.Its principle is using operational amplifier building impedance matching and to buffer, then cascade two-way shunt load equilibrium and putBig circuit.But because single channel buffers the mode amplified with two-way, the promotion in impedance matching, circuit load portfolio effect is limited,It is still awkward in the circuit weak signal measurement application in field ahead of the curve.The application guidance of LT1028 operational amplifier tables of dataPart, discloses the high performance operational amplifier amplifying circuit that a kind of gain is 1000 times, its principle be by multichannel simultaneouslyThe mode of connection reduces the voltage noise of operational amplifier.But the circuit lacks necessary buffer input signal, impedance, phaseMatch and necessary gain control adaptations function.The nonstandard numerical value resistance of high-precision low noise required for circuit simultaneously, purchase costHeight and element supply channel is unsmooth results in, the acquired and procurement risk poor controllability of element.In addition, being answered for a variety ofWith the traversal formula stock problem of required most value series of elements, the ease for use of the circuit is also greatly limited.
At present volume production plug-in type metal thin film resistor and patch printing thick-film resistor with the kind of nominal accuracy 1% the mostIt is common.If application needs the higher grade of tolerance, would generally be wanted using the metal thin film resistor of 0.1% error to reachIt asks.But the raising of the price meeting opposite 1% of the kind goes out ten times or higher.And compared with 0.1% more accurate precision metallic thin-film electroResistance, because of its manufacturing technology complexity, the mutual restriction of material volume performance, process is tedious with calibration screening for age stability test, leadsThe distinct issues in purchase cost and delivery cycle have been caused, thus using less in volume production circuit.Only in measuring instrument meterAmount correction, the field of high-precision measurement of non-cost sensitivity, which has, sporadically to be used.Meanwhile also because resistance value usually according to E24,The stationary distribution of E96, E192 mode, i.e., each order of magnitude are distributed as fixed 24,96,192 kind of numerical value.In addition resistance is in materialDifference on material, power, temperature drift, appearance and assembling mode, for any user, the even manufacturer of resistive elementSpeech, the numerical value traversal cover type volume production stock of multi items all difficult to realize.
Summary of the invention
In view of this, the purpose of the present invention is to provide the performances of the low-noise accurate amplifying circuit based on operational amplifierImproved method, this method can promote and improve noise, total harmonic distortion plus noise (THD+ based on operational amplifier amplifying circuitN) performance.
In order to achieve the above objectives, the invention provides the following technical scheme:
The performance improvement method of low-noise accurate amplifying circuit provided by the invention based on operational amplifier, including it is followingStep:
(1) impedance for obtaining signal source in application scenarios adds with the circuit output noise of required promotion, total harmonic distortionNoise, and determine gain control potentiometer numerical value and circuit gain amplifier；
(2) preset gain is selected to adjust potentiometer raw value according to signal source impedance；
(3) according to the noise of required promotion, total harmonic distortion plus noise (THD+N), selection buffering is reversely put with cascadeThe quantity n in parallel of big circuit；
(4) it according to the quantity n in parallel of selected buffering and cascade reverse amplification circuit, by the quantitative relation of 1/n, and determinesPotentiometer；
(5) basis drafts the noise using required promotion circuit, each resistance equivalence string in signal path position in selection circuitRecombiner unit quantity in parallel；
(6) it is calculated according to the gain of operational amplifier circuit, and preset gain is combined to adjust potentiometer numerical value, predetermined output impedance,Determine signal path position resistance value；If gained resistance value belongs to E24 series of values, directly carry out selecting compoundThe equivalence of element number is series-parallel compound；
(7) if gained resistance value is not belonging to E24 series of values, the serial or parallel connection group again for carrying out recombiner unit is neededConjunction obtains equivalent resistance numerical value；
(8) circuit that cascaded gain segmentation matched with cascade reverse amplification circuit with buffering is kept with output phase is addedAdaption section.
Further, the buffering is multichannel with the quantity n in parallel of cascade reverse amplification circuit.
Further, the resistive element of compound composition is metallic film quasi-resistance in the circuit.
The present invention also provides the low-noise accurate amplifying circuits based on operational amplifier, including circuit input end, multichannelBuffering and cascade reverse amplification circuit and circuit output end；The circuit input end and each buffering and cascade reverse amplification circuitInput terminal connection；Each buffering is connect with the output end of cascade reverse amplification circuit with circuit output end.
Further, each buffering and cascade reverse amplification circuit include cascade rp-op amp unit, instituteStating rp-op amp unit includes rp-op amp and resistance unit；The resistance unit and rp-op ampOutput end connection；The input terminal of the rp-op amp is connect with circuit input end；The output end of the resistance unitIt is connect with circuit output end.
Further, the rp-op amp unit includes concatenated first rp-op amp and the second reverse phase fortuneCalculate amplifier；First rp-op amp includes the first rp-op amp and first resistor unit；Described secondRp-op amp includes the second rp-op amp and second resistance unit；
The first resistor unit is connect with the output end of the first rp-op amp；The first reverse phase operation amplifierThe input terminal of device is connect with circuit input end；The output end of the first resistor unit and the second rp-op amp input terminalConnection；
The second resistance unit is connect with the output end of the second rp-op amp；The second reverse phase operation amplifierThe input terminal of device is connect with first resistor unit output end；The output end of the second resistance unit is connected with circuit output end.
Further, the buffering is used with the resistance unit in cascade reverse amplification circuit and is made of equivalent series and parallel compensated resistanceCombined resistance unit,
Further, the buffering is multichannel with the quantity n in parallel of cascade reverse amplification circuit.
Further, the resistive element of compound composition is metallic film quasi-resistance in the circuit.
The beneficial effects of the present invention are:
The performance improvement method of low-noise accurate amplifying circuit provided by the invention based on operational amplifier, passes through bufferingWith the compound composition of signal path resistance in the multi-channel parallel and circuit of cascade reverse amplification circuit, Lai Tisheng noise, total harmonic waveDistortion plus noise (THD+N) performance, significantly improves noise and distortion performance based on operation amplifier circuit, designs high propertyEnergy low noise amplifier circuit, this method adds for output noise, the total harmonic distortion of the amplifying circuit based on operational amplifier makes an uproarSound (THD+N), be mainly distorted by operational amplifier, the thermal noise of resistance, shot noise, voltage noise, current noise, Slew Rate,The characteristic that noise caused by heat distortion, load mismatch is constituted.It takes circuit input buffering and cascades the more of reverse amplification circuitRoad is in parallel, and equivalent series-parallel compound composition signal path resistance, recombiner unit resistance recomposition optimizes operational amplifier power supplyThe many kinds of measures of Voltage rails constructs extremely low distortion low-noise amplifier.
The circuit of verified this method building can utilize common NE5532APSR, LME49860MA operational amplifier,And realize that the circuit noise of nearly -20dBu is promoted under the premise of 1% precision E24 distribution values resistance of MBA 0204VG06, and0.00025% extremely low total harmonic distortion plus noise (THD+N) performance.The circuit design can be widely applied to for such asThe high code rate professional audio recording such as 32bit 768kHz, 22.4MHz DSD and playback, precision analog electric signal measurement and instrument schoolEmerging forward position application field and the sonar detection such as quasi-, biological weak electric signal perception and gravitational wave detection, seismic wave detection surpassIn accurate low-frequency analog signal amplification scene including acoustic imaging, supersonic sounding.
Detailed description of the invention
In order to keep the purpose of the present invention, technical scheme and beneficial effects clearer, the present invention provides following attached drawing and carries outIllustrate:
Fig. 1 is the performance improvement method flow diagram of amplifying circuit.
Fig. 2 is the overall schematic of buffering with the multi-channel parallel of cascade reverse amplification circuit.
Fig. 3 a is resistance unit overall schematic.
Fig. 3 b is the equivalent series-parallel complex method schematic diagram of four resistance.
Fig. 3 c is the series-parallel complex method schematic diagram of equivalence of nine resistance.
Fig. 3 d is the series-parallel complex method schematic diagram of equivalence of 16 resistance.
Fig. 4 a is that two resistance are composed in series basic resistance recombiner unit schematic diagram.
Fig. 4 b is that two resistance are composed in series resistance unit overall schematic.
Fig. 5 a is that two resistor coupled in parallel form basic resistance recombiner unit schematic diagram.
Fig. 5 b is two resistor coupled in parallel resistance unit overall schematics.
Specific embodiment
The present invention will be further explained below with reference to the attached drawings and specific examples, so that those skilled in the art can be withIt better understands the present invention and can be practiced, but illustrated embodiment is not as a limitation of the invention.
Embodiment 1
As shown in Figure 1, the performance improvement of the low-noise accurate amplifying circuit provided in this embodiment based on operational amplifierMethod, specifically includes the following steps:
(1) impedance of signal source in concrete application scene and circuit output noise, total that is required or needing to be promoted are analyzedHarmonic distortion plus noise (THD+N) performance, Lai Jinhang gain control the determination of potentiometer numerical value, circuit gain amplifier；
(2) the gain adjustment potentiometer raw value suitable according to signal source impedance selection；
(3) according to drafting using noise that is required or needing to be promoted, distortion performance, selection is buffered and the reversed amplification of cascadeThe quantity n in parallel of circuit, to realize that load balancing and the amplifier device noise contribution of circuit are reduced to original by multi-channel parallelReason reaches target；
(4) according to the quantity n in parallel upper (3) selected buffering and cascade reverse amplification circuit, by the quantitative relation of 1/n,And select the immediate numerical value kind of the low noise potentiometer of practical available stock；
(5) according to the noiseproof feature drafted using required or required promotion, select signal path position in suitable circuits eachThe series-parallel recombiner unit quantity of the equivalence that resistance is suitable for；
(6) the gain adjustment potentiometer numerical value for being calculated according to the gain of common operational amplifier circuit, and (4) being combined to obtain, and it is pre-Determine output impedance, determines signal path position resistance value；If institute's value belongs to common E24 series of values, then directly intoThe selected recombiner unit quantity of row (5) institute it is equivalent compound in series and parallel, the noise of resistance, total harmonic distortion in circuit are reduced with this and addedNoise (THD+N) contribution.
(7) such as comprising being not belonging to common E24 series of values, then the serial or parallel connection recombinant for carrying out recombiner unit is needed,To realize compared with the more accurate equivalent resistance numerical radius of E96, E192；And it is good in random resistance value to highlight the present inventionEconomy, ease for use promoted；
(8) circuit that cascaded gain segmentation matched with cascade reverse amplification circuit with buffering is kept with output phase is addedAdaption section.
Buffering provided in this embodiment and the quantity of cascade reverse amplification circuit are 2 tunnels or more, can be according to practical feelingsCondition selects 3 tunnels, 4 tunnels, 5 tunnels and 6 tunnels；Or more multichannel；And need to match input impedance by concrete application situation, operation is putThe resistance value of big device linear work load；By using the multi-channel parallel of buffering and cascade reverse amplification circuit, and thus bandThe potentiometer value come reduces, and the equivalence of multiple resistance is series-parallel compound, and the method for optimization operational amplifier supply voltage rail canImprove the nearly -20dBu of noise of circuit entirety significantly, and inhibit the distortion of circuit significantly, reach 0.0005% withInterior extremely low level, or even approach total harmonic distortion plus noise (THD+N) performance of test macro itself remnants 0.00025%.
The characteristics of actual error using modern not selected volume production resistance is in class normal distribution, passes through the equivalence of resistanceThe series-parallel compound counteracting for realizing random error improves the precision of combined resistance.Relative to single resistance, combined resistancePrecision presses 4,9,16,25---n2A compound quantity respectively can be by precision improvement to 2,3,4,5---n times.Its precision improvement is notIt is limited to the quality discrepancy limitation of the material quality of resistance, precision, volume etc..Precision resister is alleviated to a certain extentObtain difficult problem.
Further the series, parallel again of equivalent series-parallel compound basic cell resistance is combined.Ensuring that precision is not badUnder the premise of single resistance, the E24 series of values kind of low cost is timely used, is also convenient to realize compared with E96, E192Distribution closer to any resistance value covers.Largely alleviate the procurement cost and practical electricity of nonstandard numerical value resistanceContradiction between road optimization demand.
Circuit contains input resistant matching, gain control, signal phase holding function, relatively other to teach in analog circuitCircuit disclosed in section's book, operational amplifier specifications more improves feasible, can be flexibly adapted to a variety of emerging application fields in electricityDifferent demands in terms of road input impedance, gain, signal processing adaptation.
Embodiment 2
Operational amplifier that this method is easily purchased using common volume production, resistance device obtain noise, total harmonic distortion adds and makes an uproarSound (THD+N) performance is obviously improved；Utilize the common compound composition more strong noise of resistance, total harmonic distortion plus noise (THD+N) performance and precision, and covered with the numerical value that most common E24 series of values achieves over E96, E192, this method is to pass throughFollowing technical scheme is realized.
1, the load balancing that circuit is realized by being buffered in Fig. 2 with the multi-channel parallel of cascade reverse amplification circuit, reducesThe numerical value of resistance and gain control potentiometer on signal path, and then obtain the noise of circuit entirety, distortion performance promotion.It is slowThe quantity of punching and cascade reverse amplification circuit is 2 tunnels or more, and needs to put with the operation selected by specific application scenariosBig type number, design optimization goes out optimal matching input impedance, operational amplifier linear work loads corresponding R1A, R1B,R1C, the numerical value for repeating resistance R1A in structure is identical as R2A---RnA, and position R1B, R1C and so on, number in parallel depends onWiring increases bring performance degradation and influences after application purpose, estimated cost, device encapsulation and parallel connection.
2, it is suitable that the Radj element of gain control, cascaded gain segmentation and U2, R2 circuit of output phase holding is added in circuitWith part, wherein the resistance value of Radj buffers depending on physical circuit and is reduced to single channel most with the quantity for cascading reverse amplification circuitThe 1/n of good numerical value, and the volume production kind closest to numerical value is selected according to the supply position of actual components.
3, the operational amplifier in circuit by specifically should field or estimated cost, may be selected AD797, LT1028,LME49990, LME49860 and other special high performance operational amplifiers, but because buffering and cascade reverse amplification circuitMulti-channel parallel significantly reduces operational amplifier on signal path, the noise of resistance and distortion and contributes.Even if using most commonCommon, the cheap operational amplifier of NE5532/5534 one kind, can also be obtained by this method, more other using decades of times high priceThe higher noise of common low noise circuit of amplifier, total harmonic distortion plus noise (THD+N) performance.It is not limited to patch, straight cutting,The limitation of the operational amplifiers mode of appearance such as bare chip and volume size.
4, resistance is by way of Fig. 3 a, 3b, 3c and 3d on signal path in circuit, by 4,9,16---n2QuantityEquivalent series-parallel complex method is carried out to constitute.By resistance series-parallel calculation known to it is compound after numerical value there is no becomeChange.Application purpose, estimated cost are depended on for equivalent series-parallel compound resistance quantity, after device encapsulation and parallel connectionWiring, which increases bring performance degradation, to be influenced.By the long-term measurement verifying of inventor, discovery same type, kind be not selectedResistance, numeric distribution be in class Gaussian normal feature.And then find out by by random two or more resistance to go here and there,The mode of numerical value needed for compound composition in parallel (see Fig. 3 a-d).It is appointed with apparent precision/price than being promoted and being combined intoThe characteristics of meaning numerical value.Its basic reason is during having benefited from multiple compound compositions, and the probable error of each resistor random-access is because compoundAnd it offsets, and then bring the promotion of final combined resistance mean accuracy.Resistance for the compound composition of this method is not limited to goldBelonging to materials and patch, straight cutting, the limitations of the factors such as volume and numerical values recited difference such as film, oxide, carbon film can lead toIt crosses the method and can get certain mean accuracy promotion.
5, series, parallel can be carried out by way of Fig. 4 a, 4b, Fig. 5 a, 5b respectively by carrying out equivalent series-parallel resistanceComposition, on E24 and following common series of values distributed basis, easily and flexibly to obtain compared with the more nonstandard number of E96, E192The covering of value is distributed.
6, Fig. 4 a, 4b, Fig. 5 a, in 5b circuit compound composition basic resistance element R1, R2 by specifically should field or pre-It is counted as this limitation, the metallic film material resistance of the basic accuracies such as 1%, 0.1% and the high-precision, low of other customizations may be selectedThe resistance of temperature drift.But because of the random error principle of cancellation of Fig. 3 a-d, even if the 1% precision thick film print that selection is most common, cheapBrush resistance, its opposite used aloned also bring along certain precision and mention with noise, total harmonic distortion plus noise (THD+N) performanceIt rises.It is not limited to the limitation of the resistance mode of appearance such as patch, straight cutting and volume size.
Embodiment 3
It is further described combined with specific embodiments below, the low-noise accurate amplifying circuit based on operational amplifierPerformance improvement method, is implemented as follows:
Step 1, the concrete condition applied according to circuit, analyzes input and output impedance, and signal amplitude, frequency characteristic determine electricityRoad entire gain；For convenience of the comparison for carrying out circuit noise, total harmonic distortion plus noise (THD+N) performance, confirmatory experiment is draftedInput signal is the just profound wave of 1Vrms, 997Hz, and input and output impedance is 10k Ω, circuit maximum gain 20dB；
Step 2, according to the expected number for promoting target and determining buffering with cascade reverse amplification circuit, according to operational amplifierVoltage noise performance press the principle that the square root relationship of number n in parallel is promoted, number in parallel can be 2,3,4---n it is anyNumber；But the high frequency distribution parameter of consideration circuit layout, wiring influences the exploitativeness with circuit, and highest number is to be no more than 8 tunnelsIt is advisable；Confirmatory experiment is drafted as 4 tunnels；
Step 3, according to budget, and consider that the acquisition complexity of element determines that circuit uses operational amplifier, resistanceModel, material, encapsulated type；Noise, the distortion performance characteristic for considering Operational amplifier element, select the bipolarity of low noise defeatedThe high performance operational amplifier entered can get higher theoretical performance, and the dual operational amplifier of simultaneous selection patch encapsulation can be certainThe compactedness of the raising circuit of degree；But high performance J-FET input kind should be selected under the situation of high input source impedance again；Resistance is also to select the metallic film material kind of 1% or more precision to be advisable；Quasi- selected TI LME49860MA of confirmatory experiment,0204 VG06 series resistance of NE5532APSR operational amplifier and VISHAY MBA；
Step 4, according to the series-parallel compound resistance unit quantity of the certainty equivalents of preceding step；By 4,9,16---n2Quantity carry out it is compound, it is usually balanced to consider that circuit is overall, specific component encapsulation size, and the circuit board being largely connected to the network is by clothFactors, the resistance unit quantity such as office, wiring high-frequency parasitic parameter influence are chosen no more than 25；
Step 5, according to the numerical value of potentiometer, resistance in input, output characteristics counting circuit, and suitable potentiometer is chosenType kind；Consider that organic carbon membrane material in the deficiency of noise, non-linear distortion aspect of performance, preferably selects metal wound wire, slipDescription of materials；In the case where acquisition high quality potentiometer is had any problem, good linear change rate and low numerical value quality should be selected；For the application of the loudness gain such as audio class control, potentiometer high level end can be changed to the amplification output that even buffering cascades reversed unitEnd obtains equivalent Exponential Type change rate using the feedback of circuit；It is TOCOS RV30 series that confirmatory experiment, which intends selected electric potential device,；
It step 6, can be according to actual needs with two E24 series of values electricity according to the series connection of resistance and calculation method in parallelResistance is connected in series or in parallel equivalent series-parallel recombiner unit needed for mode obtains；
Step 7, the circuit connection for carrying out combined resistance uses the resistance of HP/Agilent 34401A measurement recombiner unitNumerical value；
Step 8, selected number, operational amplifier, potentiometer, resistance are completed to build, uses Audio Precision2272 audio-frequency test analyzers carry out direct circuit noise and total harmonic distortion plus noise (THD+N) is tested；The 22kHz band toleranceSystem, calibrated rear test macro remnants output noise is -119.1dBu, and THD+N≤0.00025%, 997Hz are without weighted mode.
Embodiment 4
It is buffered by 4 roads and cascades reverse amplification circuit, operational amplifier selects LME49860MA, operational amplifier power railVoltage ± 17V, 2k Ω potentiometer；Resistance R1A is compound by 4 series-parallel units of equivalence, and each recombiner unit is a 1k Ω electricityResistance；Resistance R1B is compound by 4 series-parallel units of equivalence, and each recombiner unit is by Fig. 4 a-4b by a 4.7k Ω and a 10kΩ composes in parallel the equivalent resistance of 3.2k Ω；Resistance R1C is compound by 4 series-parallel units of equivalence, and each recombiner unit is by one10 Ω resistance combinations；Circuit build normally work on power after, unit gain output state is adjusted to by potentiometer.Assess its surveyNumerical quantity and performance boost effect are shown in Table 1.
Embodiment 5
It is buffered by 4 roads and cascades reverse amplification circuit, operational amplifier selects NE5532APSR, operational amplifier power railVoltage ± 17V, 2k Ω potentiometer；Resistance R1A is compound by 4 series-parallel units of equivalence, and each recombiner unit is a 1k Ω electricityResistance；Resistance R1B is compound by 4 series-parallel units of equivalence, and each recombiner unit is by Fig. 4 a-4b by a 4.7k Ω and a 10kΩ composes in parallel the equivalent resistance of 3.2k Ω；Resistance R1C is compound by 4 series-parallel units of equivalence, and each recombiner unit is by one10 Ω resistance combinations；Circuit build normally work on power after, unit gain output state is adjusted to by potentiometer.Assess its surveyNumerical quantity and performance boost effect are shown in Table 1.
Embodiment 6
It is buffered by 4 roads and cascades reverse amplification circuit, operational amplifier selects LME49860MA, operational amplifier power railVoltage ± 17V, 2k Ω potentiometer；Resistance R1A is a 1k Ω resistance；Resistance R1B is a 3.3k Ω resistance；Resistance R1C isOne 10 Ω resistance；Circuit build normally work on power after, unit gain output state is adjusted to by potentiometer.Assess its surveyNumerical quantity and performance boost effect are shown in Table 1.
Embodiment 7
It is buffered by 4 roads and cascades reverse amplification circuit, operational amplifier selects NE5532APSR, operational amplifier power railVoltage ± 17V, 2k Ω potentiometer；Resistance R1A is a 1k Ω resistance；Resistance R1B is a 3.3k Ω resistance；Resistance R1C isOne 10 Ω resistance；Circuit build normally work on power after, unit gain output state is adjusted to by potentiometer.Assess its surveyNumerical quantity and performance boost effect are shown in Table 1.
Embodiment 8
It is buffered by 1 road and cascades reverse amplification circuit, operational amplifier selects LME49860MA, operational amplifier power railVoltage ± 17V, 10k Ω potentiometer；Resistance R1A is compound by 4 series-parallel units of equivalence, and each recombiner unit is a 1k Ω electricityResistance；Resistance R1B is compound by 4 series-parallel units of equivalence, and each recombiner unit is by Fig. 5 a-5b by a 4.7k Ω and a 10kΩ composes in parallel the equivalent resistance of 3.2k Ω；Resistance R1C is compound by 4 series-parallel units of equivalence, and each recombiner unit is by one10 Ω resistance combinations；Circuit build normally work on power after, unit gain output state is adjusted to by potentiometer.Assess its surveyNumerical quantity and performance boost effect are shown in Table 1.
Embodiment 9
It is buffered by 1 road and cascades reverse amplification circuit, operational amplifier selects NE5532APSR, operational amplifier power railVoltage ± 17V, 10k Ω potentiometer；Resistance R1A is compound by 4 series-parallel units of equivalence, and each recombiner unit is a 1k Ω electricityResistance；Resistance R1B is compound by 4 series-parallel units of equivalence, and each recombiner unit is by Fig. 5 a-5b by a 4.7k Ω and a 10kΩ composes in parallel the equivalent resistance of 3.2k Ω；Resistance R1C is compound by 4 series-parallel units of equivalence, and each recombiner unit is by one10 Ω resistance combinations；Circuit build normally work on power after, unit gain output state is adjusted to by potentiometer.Assess its surveyNumerical quantity and performance boost effect are shown in Table 1.
1 embodiment 4-11 circuit configuration difference of table and cell resistance numerical value, noise, total harmonic distortion plus noise (THD+N)Test performance result
Embodiment 10
It is buffered by 1 road and cascades reverse amplification circuit, operational amplifier selects LME49860MA, operational amplifier power railVoltage ± 15V, 10k Ω potentiometer；Resistance R1A is a 1k Ω resistance；Resistance R1B is a 3.3k Ω resistance；Resistance R1C isOne 10 Ω resistance；Circuit build normally work on power after, unit gain output state is adjusted to by potentiometer.Because not relating toAnd circuits improvement method of the invention, noise and distortion performance be it is generally horizontal, which only makees the performance ginseng of available circuitThan not covering within scope of the presently claimed invention.
Embodiment 11
It is buffered by 1 road and cascades reverse amplification circuit, operational amplifier selects NE5532APSR, operational amplifier power railVoltage ± 15V, 10k Ω potentiometer；Resistance R1A is a 1k Ω resistance；Resistance R1B is a 3.3k Ω resistance；Resistance R1C isOne 10 Ω resistance；Circuit build normally work on power after, unit gain output state is adjusted to by potentiometer.Because not relating toAnd circuits improvement method of the invention, noise and distortion performance be it is generally horizontal, which only makees the performance ginseng of available circuitThan not covering within scope of the presently claimed invention.
Embodiment 4-9 sufficiently demonstrates of the present invention, the multi-channel parallel of buffering and cascade reverse amplification circuit, current potentialDevice numerical value reduces, resistance equivalent series-parallel compound, power rail voltage optimization method bring circuit output noise, total harmonic distortionPlus noise (THD+N) performance boost, and the series, parallel again of equivalent series-parallel compound basic cell resistance combine bring moreExtensive resistance value covering.
In summary in conclusion contrast verification is adjusted through experimental demonstration repeatedly and parameter, using common1% precision E24 distribution values resistance of NE5532APSR, LME49860MA operational amplifier and 0204 VG06 of MBA, by weThe circuit of method building, it can be achieved that the circuit noise of nearly -20dBu promoted and 0.00025% extremely low total harmonic distortion plus noise(THD+N) performance.Meanwhile even if the operational amplifier common, cheap using most common NE5532/5534 one kind, can also lead toThis method acquisition is crossed, it is more other to be added using the higher noise of common low noise circuit of decades of times high price amplifier, total harmonic distortionNoise (THD+N) performance.
Finally, it is stated that the above examples are only used to illustrate the technical scheme of the present invention and are not limiting, although referring to compared withGood embodiment describes the invention in detail, those skilled in the art should understand that, it can be to skill of the inventionArt scheme carries out parameter adjustment or equivalent replacement should all cover without departing from the objective and range of technical solution of the present inventionIn protection scope of the present invention.