Patent ID: 9654074
Date: 2017-05-16
CPC Classifications: H03F,H03G

Claim:
1. A variable gain amplifier circuit, comprising: a main amplifier, for amplifying an input signal to generate an output signal; a current sensing circuit, coupled to the main amplifier, for providing a sensed current related to a current flowing through the main amplifier; a variable loading, coupled to the current sensing circuit via a node, wherein the sensed current flows through the node and the variable loading to provide a loading voltage; and a control amplifier, coupled to the node and the main amplifier, for receiving a control voltage and the loading voltage to generate an adjustment signal to control a gain of the main amplifier; wherein a resistance of the variable loading has a nonlinear relationship with the control voltage; and the variable loading comprises a plurality of circuit cells, and each of the circuit cells provides a specific current to the node, and a combination of the specific currents provided by the circuit cells is comprised of the sensed current flowing through the node and the variable loading.