Patent ID: 8018285

Claim:
A step variable gain amplifier, comprising: an amplification unit for converting and amplifying a voltage component of an input signal into a current component according to a step amplification control signal, wherein the amplification unit has a first transconductance amplifier and a second transconductance amplifier interconnected in parallel to each other, the first transconductance amplifier includes first and second transistors interconnected in series to each other, and the second transconductance amplifier includes third and fourth transistors interconnected in series to each other; a controller for generating the step amplification control signal and controlling on/off of the amplification unit according to the step amplification control signal; at least one first switching device and an attenuator connected between a driving signal input terminal of the third transistor and a reception terminal for receiving the input signal; and an output unit for outputting a voltage component corresponding to the current component, the output unit being connected to the amplification unit, wherein a driving signal input terminal of the first transistor is directly connected to the reception terminal, wherein, in a high gain mode operation, the controller is configured to turn on the first and second transistors and to turn off the third and fourth transistors, wherein, in a middle or low gain mode operation, the controller is configured to switch on the at least one first switching device, to turn off the first and second transistors, and to turn on the third and fourth transistors, and wherein the middle or low gain mode operation is determined by an attenuation ratio of the attenuator.