WIDE BAND BALANCED OUTPUT FREQUENCY MODULATOR USING A VIDEO SIGNAL AS A MODULATION SIGNAL

摘要

A frequency modulator is provided, in which, for instance, a video signal is used as a modulation signal. A differential amplifier is formed by first and second transistors. First and second load resistors are connected between respective collectors of the first and second transistors and a power supply terminal (A). A series circuit of first and second feedback capacitors is inserted between the collector of the first transistor and a base of the second transistor. A series circuit of third and fourth feedback capacitors is inserted between the collector of the second transistor and a base of the first transistor. The respective same electrodes of first and second variable capacitance diodes are connected with each other and the other electrodes thereof are connected respectively to a junction point of the first and second feedback capacitors and to a junction point of the third and fourth feedback capacitors. First and second resonance coils are connected between the respective other electrodes of the first and second variable capacitance diodes and a reference potential point. A modulation signal is applied to the same electrode junction of the first and second variable capacitance diodes, and oscillation output signals of opposite phases are obtained from the respective collectors of the first and second transistors.