| 摘要 |
PURPOSE:To achieve stable intermediate frequency amplifying circuit without self- oscillation, by inputting the final stage output of a differential amplifier of multistage constitution to the base of an emitter follower transistor (TR) via a resistor and obtaining an output from the emitter. CONSTITUTION:An FM or PM signal inputted from a terminal 1 is amplified and in amplitude-control at a differential amplifier of multistage constitution consisting of TRsQ1, Q2-Q11, Q12. The output signal from the collector of the differential amplifiers Q11, Q12 at the final stage is applied to the base of emitter follower TRsQ13, Q14 via resistors R27, R26 respectively. The output signal of the emitter of the TRsQ13, Q14 is applied to emitter followers TRsQ17, Q18 via resistors R29, R28 and an output is picked up at terminals 3, 2 from the emitter of the TRsQ17, Q18. By suitably selecting the value of the resistors R26-R29, the high frequency component of an input signal only can be attenuated without attenuating the gain of an intermediate frequency band with this resistance value and the junction capacitance of the base and collector of the emitter follower TR and a stable circuit can be obtained without self-oscillation. |
