| 摘要 |
PURPOSE:To form a double balanced modulator having an excellent modulation signal suppressing characteristic with a simple circuit by providing symmetrically two modulation circuits each having an excellent carrier suppressing characteristic. CONSTITUTION:A waveform where a modulation input S1 is superimposed on a common DC potential 19 appears at an emitter of a transistor (TR) 1. Further, TRs 3-6 connected differentially are switched by a carrier S2. Thus, the waveform extracted form collector load resistors 13-16 has a potential lower by that corresponding to a voltage drop due to a current value from current sources 25, 26 and a resistance value of load resistors 13-16 when TRs 3, 6 or TRs4, 5 are turned on. On the other hand, TRs 7, 8 and 9, 10 output a voltage inputted to their bases while selecting any of them depending on the voltage level. The two signals are added by a differential amplifier comprising TRs 11, 12 and an output signal from which a modulation signal component is eliminated completely.
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