Patent ID: 7956933
Filing Date: 2011-06-07
Classification: H03F,H03G,H04N

Abstract:
1. A tuner circuit receiving a television signal of a digital broadcast, comprising: a radio frequency amplifier having a variable gain, radio frequency amplifying said received television signal, and outputting a resultant signal; an oscillator generating a local oscillation signal at an oscillation frequency corresponding to a frequency of a desired channel; a mixing circuit mixing the signal output from said radio frequency amplifier with said local oscillation signal, frequency converting a resultant signal to a signal at an intermediate frequency, and outputting a resultant signal; an emitter follower circuit including a transistor for current amplification, having a high input impedance and a low output impedance, and current amplifying the signal output from said mixing circuit; a gain control circuit outputting a control voltage for automatically controlling the gain of said radio frequency amplifier such that the signal output from said radio frequency amplifier is kept at a certain level, in accordance with a level of the signal output from said mixing circuit; and a demodulation circuit receiving the signal output from said mixing circuit through said emitter follower circuit, digital demodulating the received signal, and generating a transport stream signal, wherein said emitter follower circuit varies a drive current of said transistor for current amplification such that a distortion level becomes small, in accordance with the control voltage output from said gain control circuit, and wherein said emitter follower circuit receives a first signal and a second signal, the first signal is the resultant signal outputted from said mixing circuit, and the second signal is the control voltage outputted from said gain control circuit.