| 摘要 |
A tuner with a radio-frequency pre-stage (1) and a mixer stage (2), provided with an oscillator signal. The mixer is formed by a transistor (12) incorporating an emitter resistor (13) in its emitter circuit. The radio-frequency signal is taken from the output of the radio-frequency pre-stage to the input of the mixer stage via a DC-biased diode (28). The DC path for the diode includes the emitter resistor of the mixer stage. The transistor and diode currents flowing through that path having the same direction of flow. The bias voltage of the diode is altered as a function of the amplitude of the unlimited intermediate-frequency signal via a control circuit (30), the direct current through the diode decreasing with increasing amplitude of the intermediate frequency signal.
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