Patent ID: 7705680
Filing Date: 2010-04-27
Classification: H03F,H03G

Abstract:
1. A gain switching low-noise amplifier circuit, comprising: an input terminal of an RF signal; a transistor C having a base to which a signal from the input terminal is inputted; a first bias circuit connected to the base of the transistor C via a resistor and turning ON the transistor C; a first transistor group including transistors A a first capacitor and a second capacitor connected to each base of the transistors of the first transistor group and the second transistor group, respectively, and short-circuited to ground at a frequency band of the RF signal in an AC manner; a first resistor and a second resistor connected to each base of the transistors of the first transistor group and the second resistor group, respectively; a second bias circuit which turns ON the first transistor group and the second transistor group via the first resistor and the second resistor, respectively; an inductor connected between collectors of N pieces of transistors from A a first switch which short-circuits between bases and emitters of the transistors of the first transistor group via the first resistor or connects the first transistor group to the second bias circuit; a second switch which short-circuits between bases and emitters of the transistors of the second transistor group via the second resistor or connects the second transistor group to the second bias circuit; a gain switching control terminal which exclusively turns ON/OFF the first switch and the second switch; and an output terminal connected to collectors of the transistors of the first transistor group, wherein collectors of N−X pieces of transistors from BX+1 to BN of the second transistor group are connected to the DC power source, wherein emitters of the transistors A wherein emitters of X pieces of transistors from B wherein emitters of N−X pieces of transistors from BX+1 to BN of the second transistor group are short-circuited and connected, the gain switching low-noise amplifier circuit further comprising: a resistor B a resistor B