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CMOS audio operational amplifier

An operational amplifier, audio technology, applied in differential amplifiers, DC-coupled DC amplifiers, improved amplifiers to reduce nonlinear distortion and other directions, can solve the problems of anti-radio frequency interference of CMOS audio amplifier circuits

Active Publication Date: 2009-07-01
SHANGHAI BEILING
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0015] In the present invention, an N-type CMOS device is added to the CMOS audio amplifier circuit in the prior art, through its isolation effect on power supply voltage fluctuations, and by means of equalizing the voltages at the folded cascode output terminals, thereby solving the problem of CMOS audio Anti-radio frequency interference problem of amplifying circuit

Method used

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Embodiment Construction

[0023] The specific implementation manner of the present invention will be described below in conjunction with the accompanying drawings. It is explained here that CMOS includes N-type CMOS (NMOS) and P-type CMOS (PMOS). Hereinafter, when the type of CMOS is particularly emphasized, it is called NMOS or PMOS. The CMOS parameter list in the specific embodiment knows its specific type.

[0024] like image 3 As shown, the CMOS audio operational amplifier of the present invention includes: folded cascode input stage, double-ended to single-ended current mirror, Class AB floating bias circuit, bias circuit, push-pull common-source output stage and an NMOS M27.

[0025] The circuit design process of the specific implementation of the audio operational amplifier of the present invention will be described in detail below.

[0026] According to the requirements of the voice-activated switching hands-free call system for the microphone amplifier, the following parameters can be set: ...

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Abstract

A CMOS audio operational amplifier comprises an input stage of a folding cascode, a double-ended-to-single-ended current mirror, a Class AB floating bias, a biasing circuit, a push-pull common source output stage and a NMOS(M27), wherein, a drain electrode of the NMOS(M27) is connected with a signal input terminal of the double-ended-to-single-ended current mirror, a grid electrode of the NMOS(M27) is connected with a voltage bias terminal of the Class AB floating bias, and a source electrode of the NMOS(M27) is connected with a signal output terminal of the input stage of the folding cascode. The invention adds the NMOS device to the CMOS audio amplifying circuit in the prior art so as to isolate the fluctuation of the power voltage, and a method for ensuring equal voltages of the output terminals of the folding cascade is used, so that the anti-RFI (radio frequency interference) problem of the CMOS audio amplifying circuit is solved. The amplifier can be applied to the field of audio operational amplification, for example, the amplifier can be used as an operational amplifying circuit of a microphone input signal in a hand-free call control circuit with sound control switching.

Description

technical field [0001] The invention relates to the field of CMOS analog integrated circuit design, in particular to a CMOS audio operational amplifier. Background technique [0002] Some audio operational amplifiers in the prior art are designed with a bipolar process, for example figure 1 The amplifier used for voice-activated switching of the microphone input signal in the hands-free call control circuit is shown, wherein: L1 is the reference voltage input terminal, transistors Q6, Q7 and resistor R2 form a current bias circuit to provide bias current for each stage; Resistor R1 and transistors Q5, Q1, Q1b, Q3, Q3b, Q2, and Q4 form a differential input stage, in which transistor Q5 is a constant current source, transistors Q1 and Q3 form a differential input pair, and transistors Q1b and Q3b are shunt tubes, so that transistor Q1 The quiescent current of Q3 and Q3 is 1 / 4*(IQ1+IQ1b), so as to obtain a suitable differential pair gain, transistors Q2 and Q4 form a current m...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H03F3/45H03F1/30H03F1/32
Inventor 张宇锋龙继志
Owner SHANGHAI BEILING