| 摘要 |
PURPOSE:To stabilize operation by providing a transistor (TR) for base current supply to TRS for constituting a current mirror circuit in a current balance type amplitude demodulator, and making a Darlington connection among TRs forming a differential DC amplifier. CONSTITUTION:An AM IF signal is inputted to an amplitude limiter 1 and a carrier level controller 3. A signal from the controller 3 is inputted to a current balance type amplitude demodulator 2 through a buffer amplifier 4. The signal obtained by the limiter 1, on the other hand, is inputted to the demodulator 2 as well. A signal v0 detected synchronously by the demodulator 2 is outputted through a low-pass filter. A differential amplifier 5 compares the signal V0 with the output of a constant voltage power source 6 to input the result to the controller 3, thereby controlling the amplification degree of the IF input signal. Then, a TRQ17 for base current supply is provided to a couple of TRs Q05 and Q14 constituting the current mirror circuit of the demodulator 2. Further, the differential amplifier 5 consists of Darlington-connected TRs Q01 and Q15, and TRs Q02 and Q16. |
