| 摘要 |
PURPOSE:To operate the modulator sufficiently even at a low operating voltage, by providing a current mirror circuit for an output stage of a differential amplifier circuit for signals to be modulated, converting the signals and inputting them to a double balanced type switch circuit. CONSTITUTION:A signal vm to be modulated is inputted to a differential amplifier circuit 1 for the signal, and the signal is converted into a current and inputted to a current mirror circuit 3 after amplification. The output current of the circuit 1 becomes a voltage variable component vD(m) of diodes Q03, Q04, is inputted to transistors (TR)Q05, Q06 and outuputted in opposite phase with each other at the collectors. The output of the circuit 3 is inputted to TRs Q07-Q10 of a double balance type switch circuit 2. A carrier wave signal vc is amplified at a differential amplifier circuit 4 for carrier waves, the output is inputted to bases of the TRsQ07-Q10, where the signals vm and vc are multiplied and the result is inputted to a load RL. Since the variable component of the signal VD(m) is far smaller than that of the signal vm, the input voltage permissible range of the signal vm is not effected by the amplitude of the vm even if the operating power supply voltage is lowered. |
