Patent ID: 10581395

Abstract:
A variable gain amplifier (1) includes: a signal transmission circuit (10, 20) including amplifying transistor units (111 to 11N, and 211 to 21N) connected in parallel between a signal input port (2P, 2N) and a signal output port (3P, 3N); a load circuit (40) connected between a supply line of power supply voltage (VDD) and an output end of the signal transmission circuit (10, 20); a signal short circuit (30) including a short-circuit transistor unit (31) connected between the supply line of the power supply voltage (VDD) and an input end of the signal transmission circuit (10, 20), a constant-current source circuit (42), and a transistor control circuit (46). The transistor control circuit (46) selects transistor units to be turned on, from among the amplifying transistor units (111 to 11N, and 211 to 21N) and the short-circuit transistor unit (31), and supplies control voltages for turning on the selected transistor units.