Patent ID: 9748911
Date: 2017-08-29
CPC Classifications: H03F,H03G

Claim:
1. A variable gain amplifying circuit for amplifying a difference between a first input signal and a second input signal to generate an amplified difference output signal, comprising: an operational amplifier having a first input terminal, a second input terminal, and an output terminal providing the amplified difference output signal; an input device having a first terminal receiving the first input signal, and a second terminal coupled to the first input terminal of the operational amplifier; and a feedback device having a first terminal coupled to the first input terminal of the operational amplifier, and a second terminal coupled to the output terminal of the operational amplifier; a dynamic biasing circuit for generating a bias current according to a set value; and a transconductance circuit for converting the difference between the first input signal and the second input signal into an analog output current flowing through the feedback device; wherein the input device has a constant resistance and the feedback device has a constant resistance; and wherein the analog output current of the transconductance circuit is varied according to the bias current.