CN102571009A - Feedforward automatic gain control circuit working in extremely low voltage current mode - Google Patents
Feedforward automatic gain control circuit working in extremely low voltage current mode Download PDFInfo
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Abstract
The invention provides a feedforward automatic gain control circuit working in an extremely low voltage current mode, and relates to the technology of sensors. The feedforward automatic gain control circuit comprises a fully differential operational amplification unit, a capacitive-resistance device, a resistor array, a control switch, rectifier, a filter, a controller, a digital reference table, a digital comparator and an add-subtract counter, wherein the fully differential operational amplification unit is used for correspondingly amplifying voltage signals of an output end of a microphone according to variation of the resistance array; the rectifier is used for converting the voltage signals into current signals and rectifying current; the filter is used for filtering the current output by the rectifier and carrying out envelop detection on input signals; the digital controller is used for comparing current output by the filter with the reference current to obtain digital control signals in the digital reference table; the digital comparator is used for comparing output of the add-subtract counter with the digital control signals, when the sound volume is in different levels, the amplifying multiple of the fully differential operational amplification unit is adjusted, so that the hearing of the auditorily handicapped is protected; when the sound volume is in a normal state, the amplifying multiple of the fully differential operational amplification unit is restored to the original value, so that the automatic gain control on the different sound volumes is realized.
Description
Technical field
The present invention relates to the microphone sensor technical field, relate to the high-precision readout circuit chip that is applicable to little acoustic-electric system (MEMS) microphone sensor, is the automatic gain control circuit of digital deaf-aid microphone reading circuit chip.
Background technology
Along with little acoustic-electric system (MEMS) continuous advancement in technology, little acoustic-electric hearing aid microphone transducer arises at the historic moment, and it has that volume is little, low in energy consumption, distortion is little and advantage such as noise resisting ability is strong, and its pairing reading circuit becomes the focus of industrial quarters research.
This transducer can equivalence be a comparatively desirable voltage source usually: very little resistance on the desired voltage subject string.But the signal of microphone micro-electro-mechanical sensors output is very faint, and generally only between μ V～mV magnitude, this design to reading circuit has proposed very harsh requirement.The noise level of reading circuit and precision have determined its minimum signal amplitude that can detect, and low noise and high-precision reading circuit are designed in order to realize high-precision key, especially under the extremely low supply voltage situation of digital microphone.
The automatic gain controlling Design of microphone reading circuit mainly can be divided into analog feedback control amplifier forward direction open-loop gain in the world at present; It is (the reference: Jones of analog feedback control amplifier bias current; Mario Martinez: " a kind of CMOS hearing aids "; Analog integrated circuit and signal processing, 21,163-172 (1999); Bake: ' a kind of low-power consumption monocycle and the control of dicyclo automatic gain ', solid-state circuit, SC-41 (9) to artificial ear; Pp.1983-1996; 2006) and analog feedback control the gate source voltage (reference: Huo Man: " a kind of low noise CMOS automatic gain control ", solid-state circuit, SC-27 (7) of controlled metal-oxide-semiconductor equivalent resistance; Pp.974-981,1992; Jin Shuyong: " a kind of efficient analog front end circuit of inferior 1V digital deaf-aid ", solid-state circuit, SC-41 (4); Pp.876-882,2006.) and the mutual conductance of current-mode FEEDBACK CONTROL metal-oxide-semiconductor (reference: lattice draw the Leix: " low pressure subthreshold value index amplifies and automatic gain control ", circuit; Device and system; Vol.152, No.1, Feb 2005) two kinds of schemes.And above automatic gain control circuit obtains to use widely in simulation hearing aids field.But the former shortcoming is its linearity and can receives the restriction of technology and supply voltage, and is special under the lower situation of supply voltage.The advantage of analog feedback is that its signal has stronger continuity.But the difficult point of analog feedback is the realization of the amplifier output accuracy of low-voltage.Usually the multiplication factor of amplifier has realized comparatively ideal precision under the control of analog feedback, and realizes that in integrated circuit very high precision is extremely difficult, needs complicated compensating circuit or very large power consumption usually.The shortcoming of current-mode feedback system is that amplifier itself does not have negative feedback structure, thereby system is lower to the precision of signal processing.And digital deaf-aid requires reading circuit to have extraordinary reading accuracy, and this has proposed challenge for the design of reading circuit.
Summary of the invention
The objective of the invention is to disclose a kind of utmost point low supply voltage current-mode feedforward automatic gain control circuit that works in; It is the microphone reading circuit of current-mode feedforward; To overcome the deficiency of prior art; Not only can effectively realize the function of automatic gain control, more through adopting the high accuracy under the passive resistance array realization utmost point low-voltage to read.Possess simultaneously under the low supply voltage work, along with the increase of volume, power consumption reduces thereupon, reaches the function that the power consumption high efficiency is utilized.The present invention provides the automatic gain control reading circuit of a kind of high accuracy, low-voltage for the digital deaf-aid microphone.
For achieving the above object, technical solution of the present invention is:
A kind of utmost point low supply voltage current-mode feedforward automatic gain control circuit that works in is used for hearing aids; It comprises: fully differential amplifier unit, appearance resistance device, electric resistance array, array control switch, rectifier, filter, digital reference table, digitial controller, digital comparator and forward-backward counter;
One fully differential amplifier unit is used for the amplification to microphone output signal;
Two inputs of fully differential amplifier unit hold the resistance device through two respectively and link to each other with ground with the microphone output, in order to constitute the high-pass filtering to input signal;
Two electric resistance arrays respectively cross-over connection between two outputs of fully differential amplifier unit, two inputs, in order to confirm the yield value of fully differential amplifier to signal;
Two electric resistance array control switchs are connected to two electric resistance array one sides respectively, in order to the yield value of control fully differential amplifier unit;
One rectifier is used for microphone output small-signal is carried out rectification;
A rectifier and a filter constitute the envelope detected circuit, in order to rectified signal is carried out the energy that filtering obtains detecting microphone output signal;
One digitial controller compares the output valve and the reference level of peak detection circuit;
One digital reference table is in order to search corresponding digital reference sign indicating number;
One forward-backward counter is in order to compression and the recovery of automatic gain control to signal;
One digital comparator, the control forward-backward counter adds reducing, and its output encoder and reference encoder with forward-backward counter compares with output compression and the enable logic of recovering.
Described current-mode feedforward automatic gain control circuit; Its physical circuit is following: first and second inputs of fully differential amplifier unit hold the resistance device through first and second respectively and link to each other with the microphone output with ground; The first electric resistance array cross-over connection is in the first input end and second output of fully differential amplifier unit, and the second electric resistance array cross-over connection is in second input and first output of fully differential amplifier unit; The first electric resistance array control switch cross-over connection is in first electric resistance array and fully differential amplifier unit one output, and the second electric resistance array control switch cross-over connection is in second electric resistance array and another output of fully differential amplifier unit;
The rectifier input connects the microphone output, and rectifier order and low pass filter, digitial controller, digital reference table, digital comparator one input are electrically connected, and another output of digitial controller is electrically connected with fully differential amplifier unit;
The forward-backward counter input is electrically connected with two clocks, digital comparator two outputs respectively, and the forward-backward counter output is electrically connected with another input of the first array control switch, the second array control switch, digital comparator respectively.
Described current-mode feedforward automatic gain control circuit, its said fully differential amplifier unit according to the different adjustment bias current of multiplication factor, makes under the bigger situation of volume the amplifier power consumption is reduced; Wherein, M1, the M2MOS pipe works in sub-threshold region, makes constant bandwidth.
Described current-mode feedforward automatic gain control circuit; Its said rectifier and filter; Under the utmost point low supply voltage of 0.8V, the small-signal more than the 100uV of microphone output is carried out rectification and filtering, and the transmission signals of rectifier and filter is the current-mode signal; The M8 of filter circuit, the M9MOS pipe works in sub-threshold region.
Described current-mode feedforward automatic gain control circuit, its said digitial controller under the utmost point low supply voltage of 0.8V, carries out logic control output to the small-signal more than the 100uV of microphone output.
A kind of utmost point low supply voltage current-mode feedforward automatic gain control circuit that works in of the present invention; It is the automatic gain control reading circuit that can be used for the current-mode feedforward of digital deaf-aid; It is digital controlled signal that its mode through feedforward makes the power conversion of microphone output signal; Thereby by digital control circuit controlling resistance array the gain of amplifier is controlled, effectively solved the problem of its continuity and precision.Circuit of the present invention be applicable to the very low operation supply voltage (as; 0.8V it is following); It helps to provide a kind of low-voltage; Low-power consumption and the high-precision reading circuit that is used in the portable digital hearing aids have been realized the method for automatic ride gain digital feed forward and the circuit of under low-voltage, working accordingly.
Description of drawings
Fig. 1 is the utmost point low supply voltage current-mode feedforward automatic gain control circuit figure that works in of the present invention, wherein, and the main element label declaration:
Fully differential amplifier unit 1 first holds resistance device 2
Second holds resistance device 3 first electric resistance arrays 4
Second electric resistance array, 5 first electric resistance array control switchs 6
The second electric resistance array control switch, 7 rectifiers 8
Forward-backward counter 13;
Fig. 2 is for working in the fully differential discharge circuit figure of utmost point low supply voltage among the present invention;
Fig. 3 is for working in the rectifier circuit figure of utmost point low supply voltage among the present invention;
Fig. 4 is for working in the filter circuit figure of utmost point low supply voltage among the present invention;
Fig. 5 is for working in the digitial controller circuit diagram of utmost point low supply voltage among the present invention.
Embodiment
The present invention has provided a kind of utmost point low supply voltage current-mode feedforward automatic gain control circuit that works in; Work in the circuit module of low supply voltage through employing, the mode of current-mode feedforward and Digital Circuit Control efficiently solves the nonlinear problem of prior art existence.
The present invention carries out high pass by holding 2,3 pairs of microphone direct current signals of resistance device, and filtering microphone direct current signal is read the microphone small-signal by fully differential discharge circuit 1; The energy of the while rectifier 8 and the envelope detected electric circuit inspection microphone small-signal of filter 9 compositions; 11 pairs of energy of digitial controller are handled and are obtained digital controlled signal; Digital reference table 10 is found corresponding gain controlling sign indicating number according to digital controlled signal, is applied to digital comparator 12, obtains enable signal; Realize the plus-minus counting function of forward-backward counter 13, promptly realized the function of Signal Compression and recovery.Plus-minus counting is synchronous with clock 22 and 33 respectively.And the corresponding different gain controlling sign indicating number of alternative sounds magnitude, final amplifier gain is realized through electric resistance array 4,5 and electric resistance array control switch 6,7 controlling resistance arrays 4,5 by the gain controlling sign indicating number.
This circuit is owing to adopt the mode of electric resistance array to realize that but high-precision wheat wind signal is read under the low supply voltage, and simultaneously through current feed-forward, numerically controlled mode has realized the automatic gain control under the low supply voltage.
Fig. 1 is the utmost point low supply voltage current-mode feedforward automatic gain control circuit that works in of the present invention.Automatic gain control circuit is divided into following components, comprising: fully differential amplifier unit 1, appearance resistance device, electric resistance array, array control switch, rectifier 8, filter 9, digital reference table 10, digitial controller 11, digital comparator 12 forward-backward counters 13;
Fully differential amplifier unit 1 first and second input holds resistance device 2,3 through first and second respectively and links to each other with the microphone output together; 4 cross-over connections of first electric resistance array are in fully differential amplifier unit 1 first input end and second output; 5 cross-over connections of second electric resistance array are 1 second input and first output in fully differential amplifier unit; 6 cross-over connections of the first electric resistance array control switch are in first electric resistance array 4 and fully differential amplifier unit 1 output, and 7 cross-over connections of the second electric resistance array control switch are in the second electric resistance array unit 5 and fully differential amplifier unit 1 output.Rectifier 8 inputs connect microphone input, output order and low pass filter 9, digitial controller 11, digital reference table 10, digital comparator 12 inputs and are electrically connected, and digitial controller 11 another outputs are electrically connected with fully differential amplifier unit 1.Forward-backward counter 13 inputs are electrically connected with two clocks 22,33, digital comparator 12 outputs respectively, and forward-backward counter 13 outputs are electrically connected with another input of the first array control switch 6, the second array control switch 7, digital comparator 12 respectively.
With reference to figure 2; In practical application, consider that the bias current of fully differential amplifier unit 1 is designed to programmable offset current source 14 under lower supply voltage and the lower power consumption; It is controlled by digitial controller 11; And the difference input is to M1, and the M2MOS pipe is operated in sub-threshold region 15, has adopted the circuit topological structure of cascade simultaneously.This circuit possesses the common mode output detection circuit simultaneously, common mode input detecting circuit and the function that under the bigger situation of volume, the amplifier power consumption is reduced.Because exporting too high causing, common mode output level transient state imports the common-mode input range that common mode electrical level exceeds amplifier in order to prevent; Among Fig. 2; By M6, M7, M8; M12, the input common mode testing circuit that the M13MOS pipe constitutes will make the input common mode electrical level beginning track of fully differential amplifier follow the tracks of in the output common mode level.And the output common mode level is by M9, M10, and M11, M14, the output common mode feedback control loop that the M16MOS pipe constitutes is confirmed.When level of sound volume not simultaneously, digitial controller is to by M3, M4, M5, M6, the programmable offset current source that the M11MOS pipe constitutes reduces or increases, thereby reaches the purpose with high efficiency fully differential amplifier, its gain bandwidth is:
ω
AGC＝β
iω
OTA＝β
ig
m/C
comp
β wherein
iBe the fully differential feedback factor, by feedback loop decision, g
m, C
CompBe M1, the mutual conductance and the fully differential amplifier building-out capacitor of M2MOS pipe.Because M1, the M2MOS pipe works in sub-threshold region, then can realize the Linear Control of mutual conductance is realized constant-gain bandwidth under the different gains.
The output signal of microphone carries out rectification by rectifier to it simultaneously, with reference to figure 3.Consider that this rectifier is operated in the low supply voltage state, this rectifier adopts current-mode circuits cascading form, promptly adopts capacitance-resistance C, and it is electric current that R makes voltage transitions, respectively the forward current and the negative current of conversion is carried out rectification with two cascade feedback control loops simultaneously.Its pipe all works in the saturation region, can bear minimum operating voltage to be:
V
DD-MIN＝2
VGS-V
TH
V wherein
GSBe metal-oxide-semiconductor gate source voltage, V
THBe the metal-oxide-semiconductor threshold voltage.
Among Fig. 3, the feedback control loop that the forward electric current is carried out rectification is by M1, M2, and M3, M4MOS manages formation, and it strides resistance amplifier structure for voltage-to-current is degenerative, and purpose makes electric current to flow into for reducing the input resistance of striding the resistance amplifier.This input impedance of striding the resistance amplifier can be confirmed by following formula:
G in the formula
Md, g
MgBe respectively the grid mutual conductance of pipe, leak mutual conductance, C
CompBe building-out capacitor.
The feedback control loop that negative current is carried out rectification is by M5, M6, and M7, M8MOS manages formation, and when electric current is negative current, signal will carry out rectification, C to negative current through forward current feedback loop cascade negative current feedback loop
Comp1Building-out capacitor for the negative current feedback loop.For the response time that makes the forward current rectification equates C with the response time of negative current rectification
CompWith C
Comp1Relation can confirm by following formula:
I in the formula
BiasWith I be respectively M4, the bias current of M5MOS pipe.This rectified signal is obtained the energy signal of input current by filter filtering subsequently.This filter has adopted the filtering mode of current-voltage-electric current that this rectified current signal is carried out filtering, with reference to figure 4.M6, M7, M8, M9; The M10MOS pipe constitutes the core circuit of filter, and it is similar to traditional active amplifier filter circuit, and different is; The M8 of this circuit, the M9MOS pipe works in sub-threshold region. and for the electric current of accurate mirror image M1 and M2, the relation that in circuit, adds buffer 1. its input and output does
The parameter that discharges and recharges for control capacittance C of I wherein.
Among Fig. 4, M1, the M2MOS pipe plays the function of current-voltage and voltage-to-current conversion respectively.M1, the M2MOS pipe works in sub-threshold region.In conjunction with above relational expression, can obtain whole filter-the cut-off frequency expression formula of 3dB does
After obtaining the energy of filtered circuit,, can relatively obtain through digitial controller with reference level in order to wait until digital control reference code.
Digitial controller is with reference to figure 5, its utilize the prime current-mode output and reference current I1-8 relatively obtain the logic control level, obtain being used for the control code 18 of adjusting of control code 17 and the fully differential amplifier bias current of digital circuit then by encoder 16.And reference current is obtained by identical rectifier 8 and filter 9.Its objective is in order to prevent the influence of process corner (PVT) reference stream.Simultaneously in order to prevent that digitial controller 11 from vibrating in critical condition, uses I
0As the sluggish electric current of digitial controller 11, to guarantee the steady operation of digitial controller 11.
Digital comparator provides the enable signal of forward-backward counter plus-minus.And forward-backward counter provides the control code signal of control amplifier electric resistance array.When volume is become when high-grade by inferior grade, when automatic gain control circuit compressed signal, counter was for subtracting counting operation, and when reducing to the reference encoder of appointment, digital circuit will make counter stop to subtract counting through digital comparator output enable signal; When volume is become when high-grade by high-grade, automatic gain control circuit will recover or remain to initial value signal.Practical implementation can make counter stop to add counting through digital comparator output enable signal and accomplish.
Can know that from above description the utmost point low supply voltage current-mode feedforward automatic gain control circuit that works in of the present invention links to each other the output of microphone with automatic gain control closed loop amplifier input, simultaneously the microphone output is linked to each other with the input of rectifier.Ratio by the fully differential amplifier is pressed electric resistance array with the output voltage of microphone is realized the amplification to it.Simultaneously in order to obtain the corresponding different digital controlled signal of different volume ranks; Need microphone output signal is carried out quantification treatment; At first by rectifier the microphone output voltage signal is carried out rectification, its rectification output signal carries out the input signal energy that filtering obtains by filter to it.Energy signal compares processing by digitial controller and reference level, obtains digital controlled signal, on the digital reference table, finds out other digital reference coding of diaphone magnitude by digital controlled signal.When volume was the normal quantity rank, counter was not worked, and signal normally amplifies; From the amount of bass rank toward the transition of louder volume rank the time, counter is for subtracting counting, and counter subtracts this reference encoder state now that count down to by a last encoding state, and then the multiplication factor of fully differential amplifier realizes the compression to signal from large to small.From the louder volume rank when the amount of bass level transition, counter is for adding counting, counter is added by a last encoding state and count down to this reference encoder state now, then the multiplication factor of fully differential amplifier is changed from small to big, and realizes the recovery amplification to signal.Encode when identical when counter output encoder and digital reference, stop to add counting and subtracting counting of counter.The yield value of automatic gain control is encoded next definite by the digital reference in the digital reference table, the realization volume is encoded at the corresponding different digital reference of different brackets: this has just realized the function that microphone reading circuit is controlled according to the rank realization automatic gain of volume.
More than be to the utmost point low supply voltage current-mode feedforward automatic gain control circuit that works in of the present invention; Make microphone work in the description of the execution mode of utmost point low supply voltage current-mode feedforward automatic gain control; To one skilled in the art, some advantage that has obtained this circuit is conspicuous.Also should be appreciated that in scope of the present invention and spirit and can carry out various changes, modification and alternative embodiment.The protection range that protection scope of the present invention delimited by claims fully is a boundary.
Claims (5)
1. one kind works in utmost point low supply voltage current-mode feedforward automatic gain control circuit, is used for hearing aids; It is characterized in that, comprising: fully differential amplifier unit, appearance resistance device, electric resistance array, array control switch, rectifier, filter, digital reference table, digitial controller, digital comparator and forward-backward counter;
One fully differential amplifier unit is used for the amplification to microphone output signal;
Two inputs of fully differential amplifier unit hold the resistance device through two respectively and link to each other with ground with the microphone output, in order to constitute the high-pass filtering to input signal;
Two electric resistance arrays respectively cross-over connection between two outputs of fully differential amplifier unit, two inputs, in order to confirm the yield value of fully differential amplifier to signal;
Two electric resistance array control switchs are connected to two electric resistance array one sides respectively, in order to the yield value of control fully differential amplifier unit;
One rectifier is used for microphone output small-signal is carried out rectification;
A rectifier and a filter constitute the envelope detected circuit, in order to rectified signal is carried out the energy that filtering obtains detecting microphone output signal;
One digitial controller compares the output valve and the reference level of peak detection circuit;
One digital reference table is in order to search corresponding digital reference sign indicating number;
One forward-backward counter is in order to compression and the recovery of automatic gain control to signal;
One digital comparator, the control forward-backward counter adds reducing, and its output encoder and reference encoder with forward-backward counter compares with output compression and the enable logic of recovering.
2. current-mode feedforward automatic gain control circuit as claimed in claim 1; It is characterized in that; Physical circuit is following: first and second inputs of fully differential amplifier unit hold the resistance device through first and second respectively and link to each other with the microphone output with ground; The first electric resistance array cross-over connection is in the first input end and second output of fully differential amplifier unit, and the second electric resistance array cross-over connection is in second input and first output of fully differential amplifier unit; The first electric resistance array control switch cross-over connection is in first electric resistance array and fully differential amplifier unit one output, and the second electric resistance array control switch cross-over connection is in second electric resistance array and another output of fully differential amplifier unit;
The rectifier input connects the microphone output, and rectifier order and low pass filter, digitial controller, digital reference table, digital comparator one input are electrically connected, and another output of digitial controller is electrically connected with fully differential amplifier unit;
The forward-backward counter input is electrically connected with two clocks, digital comparator two outputs respectively, and the forward-backward counter output is electrically connected with another input of the first array control switch, the second array control switch, digital comparator respectively.
3. current-mode feedforward automatic gain control circuit as claimed in claim 1 is characterized in that said fully differential amplifier unit according to the different adjustment bias current of multiplication factor, makes under the bigger situation of volume the amplifier power consumption is reduced; Wherein, M1, the M2MOS pipe works in sub-threshold region, makes constant bandwidth.
4. current-mode feedforward automatic gain control circuit as claimed in claim 1; It is characterized in that; Said rectifier and filter; Under the utmost point low supply voltage of 0.8V, the small-signal more than the 100uV of microphone output is carried out rectification and filtering, and the transmission signals of rectifier and filter is the current-mode signal; The M8 of filter circuit, the M9MOS pipe works in sub-threshold region.
5. current-mode feedforward automatic gain control circuit as claimed in claim 1 is characterized in that, said digitial controller under the utmost point low supply voltage of 0.8V, carries out logic control output to the small-signal more than the 100uV of microphone output.
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| CN104183241A (en) * | 2013-05-28 | 2014-12-03 | 无锡华润矽科微电子有限公司 | Control circuit and method for improving volume adjustment of audio signal |
| CN104660194A (en) * | 2015-03-06 | 2015-05-27 | 东南大学 | Four-input transconductance amplifier for fully differential Gm-C filter |
| CN105915192A (en) * | 2016-05-25 | 2016-08-31 | 东南大学 | Stepping-type automatic gain control system |
| CN106533276A (en) * | 2016-12-07 | 2017-03-22 | 天津易哲微电子技术有限公司 | Method and circuit for detecting position of servo motor |
| CN107317563A (en) * | 2017-08-21 | 2017-11-03 | 四川西南交大铁路发展股份有限公司 | A kind of difference selection filter circuit and method |
| CN107408921A (en) * | 2015-02-27 | 2017-11-28 | Tdk株式会社 | For the integrated circuit arrangement of microphone, the method for microphone system and one or more circuit parameters for adjusting microphone system |
| CN107426125A (en) * | 2016-05-24 | 2017-12-01 | 德克萨斯仪器股份有限公司 | Envelope detector based on fast current |
| CN111490739A (en) * | 2019-01-25 | 2020-08-04 | 杭州海康威视数字技术股份有限公司 | Device and equipment for amplifying audio signal |
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| CN104183241A (en) * | 2013-05-28 | 2014-12-03 | 无锡华润矽科微电子有限公司 | Control circuit and method for improving volume adjustment of audio signal |
| CN104183241B (en) * | 2013-05-28 | 2017-09-29 | 无锡华润矽科微电子有限公司 | Improve the control circuit and method of audio signal volume regulation |
| CN107408921B (en) * | 2015-02-27 | 2021-02-26 | Tdk株式会社 | Integrated circuit arrangement for a microphone, system and method for adjusting a parameter |
| CN107408921A (en) * | 2015-02-27 | 2017-11-28 | Tdk株式会社 | For the integrated circuit arrangement of microphone, the method for microphone system and one or more circuit parameters for adjusting microphone system |
| CN104660194A (en) * | 2015-03-06 | 2015-05-27 | 东南大学 | Four-input transconductance amplifier for fully differential Gm-C filter |
| CN107426125B (en) * | 2016-05-24 | 2021-10-29 | 德克萨斯仪器股份有限公司 | Envelope detector based on fast current |
| CN107426125A (en) * | 2016-05-24 | 2017-12-01 | 德克萨斯仪器股份有限公司 | Envelope detector based on fast current |
| CN105915192A (en) * | 2016-05-25 | 2016-08-31 | 东南大学 | Stepping-type automatic gain control system |
| CN106533276A (en) * | 2016-12-07 | 2017-03-22 | 天津易哲微电子技术有限公司 | Method and circuit for detecting position of servo motor |
| CN106533276B (en) * | 2016-12-07 | 2019-09-06 | 芯愿景软件有限公司 | A kind of method and circuit of servo motor position detection |
| CN107317563A (en) * | 2017-08-21 | 2017-11-03 | 四川西南交大铁路发展股份有限公司 | A kind of difference selection filter circuit and method |
| CN107317563B (en) * | 2017-08-21 | 2024-02-13 | 四川西南交大铁路发展股份有限公司 | Differential selection filter circuit and method |
| CN111490739A (en) * | 2019-01-25 | 2020-08-04 | 杭州海康威视数字技术股份有限公司 | Device and equipment for amplifying audio signal |
| CN111490739B (en) * | 2019-01-25 | 2023-09-26 | 杭州海康威视数字技术股份有限公司 | Device and equipment for amplifying audio signal |
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| CN102571009B (en) | 2014-04-23 |
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