Patent ID: 7446609
Filing Date: 2008-11-04
Classification: H03G

Abstract:
1. A gain adjusting circuit applied to a variable gain amplifier, the gain adjusting circuit comprising: a linear exponential transforming circuit for receiving a linear controlling signal and transforming the linear controlling signal to output an exponential controlling signal; a voltage buffer circuit, which is coupled with the linear exponential transforming circuit to receive the exponential controlling signal, and outputs a feedback signal according to the exponential controlling signal and a bias current while outputting a voltage controlling signal to control the variable gain amplifier; and a power transforming circuit, which is coupled with the linear exponential transforming circuit and the voltage buffer circuit to receive the exponential controlling signal and the feedback signal, and to take two times of a square root of a product of the exponential controlling signal and the feedback signal plus the bias current to output a power signal to the linear exponential transforming circuit.