Suppressed carrier modulator using differential amplifier

DETAILED DESCRIPTION Accordingly, it is an object of this invention to provide a novel suppressed carrier modulation system having a large dynamic range even with a low source voltage.
Another object of this invention is to provide an improved suppressed carrier modulation system which can readily be fabricated with an integrated circuit for providing sufficient reduction in the carrier leak without relying on sophisticated adjustments.
According to this invention, there is provided a suppressed carrier modulation system comprising first, second, third and fourth transistor pairs with emitters of each pair coupled; fifth and sixth transistor pairs with emitters of each pair coupled; a differential amplifier; means for connecting base electrodes of the transistors of the fifth transistor pair to respective emitter electrodes of the first and second transistor pairs; means for connecting base electrodes of the transistors of the sixth transistor pair to respective emitter electrodes of the third and fourth transistor pairs; means for connecting emitter electrodes of the fifth and sixth transistor pairs to a pair of input terminals of the differential amplifier, respectively; means for applying a clamped modulation signal to a base electrode of a first transistor of the first transistor pair and to a base electrode of a second transistor of the fourth transistor pair; means for applying a signal to be modulated to base electrodes of respective second transistors of the first and third transistor pairs; means for applying direct current voltage to a base electrode of the second transistor of the second transistor pair and to a base electrode of the first transistor of the third transistor pair; and means for applying a signal to be modulated to respective base electrodes of the first transistors of the second and fourth transistor pairs, the last mentioned signal to be modulated having a phase opposite to that of the first mentioned signal to be modulated supplied to the respective base electrodes of the second transistors of the first and third transistor pairs, thereby producing a suppressed carrier modulated output signal on an output terminal of the differential amplifier