| 摘要 |
PURPOSE:To stabilize an output by providing the 2nd differential amplifier, a circuit which synthesizes the 1st-4th signals and obtains a phase variable output signal and a control means which controls together all current sources of the 1st-4th differential amplifiers in common in the same manner and changes the phase of a phase variable output signal. CONSTITUTION:In a variable phase shifting circuit adding vectors through the use of four-phase input signals with phase differences of 90 deg., a common phase shifting control signal controls the current sources S1-S4 of the differential amplifiers D1-D4 so that all four-phase input signals can be amplitude- controlled by the control signal. With Vc (control voltage) = Vr (reference voltage) given, all currents of a current source 22 are set so that they can flow in a transistor Q21. The current division ratio of the current of a current source 21 is changed by varying the control voltage Vc, which means that the variable current sources S1-S4 are simultaneously controlled. Thus a variable phase shifting circuit can be obtained which easily sets the variable range for shifting a phase to 180 deg. and can obtained a stable output without a critical change in the amplitude of said output corresponding to the control.
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