Invention Grant
US07956933B2 Tuner circuit and digital broadcast receiver with low distortion performance and low power consumption 失效
调谐器电路和数字广播接收机具有低失真性能和低功耗

Tuner circuit and digital broadcast receiver with low distortion performance and low power consumption
Abstract:
In a tuner circuit, an automatic gain control circuit generates an RF-AGC voltage for automatically controlling a gain of an RF-AGC amplifier in accordance with a level of a signal output from an IF amplifier. An emitter follower circuit includes a transistor for current amplification, and varies a drive current of the transistor in accordance with the RF-AGC voltage. Thus, when an interference signal is at a high level, the drive current of the transistor becomes large. Therefore, distortion performance of the emitter follower circuit is improved. On the other hand, in a normal state where the interference signal is at a low level, the drive current of the transistor fails to become large. Therefore, low power consumption is achieved.
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