Patent ID: 7692491
Filing Date: 2010-04-06
Classification: H03F

Abstract:
1. A radio-frequency multistage power amplifier using hetero bipolar transistors of which emitters are connected to ground, the radio-frequency multistage power amplifier comprising: a first amplification stage including a first hetero bipolar transistor of which collector output is detected; a second amplification stage which is prior to the first amplification stage and includes a second hetero bipolar transistor in which the detection result is reflected; a first resistor provided between a collector of the second hetero bipolar transistor and a power supply; and a protection circuit which is connected between a collector of the first hetero bipolar transistor and the collector of the second hetero bipolar transistor, detects output from the collector of the first hetero bipolar transistor, and reduces a voltage of the collector of the second hetero bipolar transistor in accordance with the detected output.