| 摘要 |
PURPOSE:To increase the reliability of a tuning point indicator of an FM receiver, by applying an input signal to a transistor (TR) of a differential amplifier via a resistor and controlling the phase with a time constant determined with the resistor and an input capacitance of the TR. CONSTITUTION:An FM signal from terminals 1, 2 is inputted to the base of a differential amplifier consisting of TRs Q1, Q4 and TRs Q2, Q3 via resistors R4-R7. Emitters of the TRs Q1-Q4 are in common connection and connected to a current source I1, and the output of the differential amplifier consisting of the TRs Q1, Q4 is applied to the base of a double balancing differential amplifier consisting of TRs Q5-Q8 via a phase shifter 3 and emitter followers TRQ9, Q10. Values of the resistors R4-R7 are selected, and phase control is made with a time constant determined the values and the input capacitances of the TRs Q1-Q4, allowing to delay the phase between the collector current of the TRs Q2, Q3 and the switching operation of the TRs Q5-Q8 by pi/2. Thus, the FM signal carrier and the tuning frequency of the phase shifter 3 is allowed to coincide and the tuning point indicator points out the center correctly at tuning. |
