Patent ID: 8907724

Claim:
A variable gain amplifier, comprising a fitted differential module group and an offset voltage output module, wherein: the fitted differential module group is configured to output, under control of a driving voltage and offset voltages, an output current of the variable gain amplifier according to a reference current; the fitted differential module group includes a number n fitted differential modules, and the number n is any positive integer larger than 1; and the n fitted differential modules are cascaded in turn and meet the following: I out ( s− 1)= I in ( s ), wherein s is larger than 1 and smaller than or equal to the number n, I out (s−1) indicates an output current of an (s−1) th fitted differential module, I in (s) indicates an input current of an s th fitted differential module, an input current I in (1) of a first fitted differential module of the fitted differential module group is the reference current, and an output current of an n th fitted differential module of the fitted differential module group is the output current of the variable gain amplifier; and the offset voltage output module is configured to input the offset voltages, to the multiple fitted differential modules, respectively, wherein the offset voltages meet: V 2 −V 1 = . . . =V s −V s-1 . . . =V n −V n-1 , wherein V s indicates an offset voltage that the offset voltage output module inputs to the s th fitted differential module.