| 摘要 |
PURPOSE:To reduce distortion at the inputting time of a high power signal, by reducing the current from a transistor (TR) which supplies current to a differential amplifier, and also reducing the current of a TR which supplies a current to a frequency converting circuit when the input signal is increased. CONSTITUTION:At the inputting time of a high power signal, DC voltage is increased at the emitters of AM detecting TRs 401, 402 and the base of a TR 411, the TR411 is gradually disconnected and a TR412 is conducted. Then, a resistor 412 is conducted. Consequently the voltage drop of a resistor 413 is increased, a TR305 is conducted and a TR306 is disconnected. Since the current is reduced at the TRs 301, 302 of an intermediate frequency amplifier 3, the gain of an intermediate frequency signal is reduced and an AGC effect corresponding to the DC voltage of a detected output can be obtained by the voltage drop of a resistor 331 between both the emitters of TRs 305, 306, so that the output voltage of the resistor 413 is made high in accordance with the voltage drop of the resistor 331. |
