Patent ID: 7868810
Filing Date: 2011-01-11
Classification: H03F,H03M

Abstract:
1. An amplifier circuit that amplifies an input signal and outputs the amplified signal from an output node, the amplifier circuit comprising: a current source that is connected between a first reference voltage line and the output node, and that generates a constant current when a switching control signal takes a first value, and does not generate the constant current when the switching control signal takes a second value; a voltage control current source which is connected to a second reference voltage line, and whose amount of current is controlled by the input signal; a cascode transistor that outputs the amplified signal, and that has a drain electrode and a source electrode, the drain electrode being connected to the current source and the output node and the source electrode being connected to the voltage control current source; a boost amplifier that has an input terminal and an output terminal, the input terminal being connected to the source electrode of the cascode transistor and the output terminal being connected to a gate electrode of the cascode transistor; a first switch that is connected between the output node and the second reference voltage line, and that is turned off when the switching control signal takes the first value and is turned on when the switching control signal takes the second value; and a second switch that is connected between the output terminal of the boost amplifier and a voltage line having a predetermined voltage, and that is turned on for a predetermined period of time when a value of the switching control signal is switched from the second value to the first value and is turned off after the predetermined period of time has elapsed.