Patent ID: 7429893

Claim:
A variable gain amplifier (VGA) comprising: a gain controlling circuit comprising: a variable current circuit, wherein the variable current circuit provides a corresponding reference current according to a control signal, such that the reference current further corresponds to the control signal; and a differential current circuit, wherein the differential current circuit divides the reference current into a load current and an input-control current according to the control signal, such that the sum of the load current and the input-control current equals the reference current, and the difference of the load current and the input-control current is controlled by the control signal; and a gain cell comprising: a load circuit for providing an active load, wherein the load circuit is biased by a load end current, such that the value of the load end current corresponds to the value of the load current; and an input circuit connects to the load circuit, receives an input signal, and establishes an output signal on the load circuit, wherein the input circuit is further biased by an input-control end current, such that the value of the input-control end current corresponds to value of the input-control current.