| 摘要 |
PURPOSE:To ensure the satisfactory control of phase with a simple constitution for a secondary active filter device consisting of two integrators and a feedback circuit, by obtaining two outputs having 90 deg. phases at both input and output sides of an integrator and at the same time controlling the time constant of either one of both integrators. CONSTITUTION:The signals having 90 deg. phases are extracted at output terminals 26a, 26b, 27a and 27b of differential circuits 23 and 24. The collector of a transistor TR141 of the preceding stage is connected to a current source 151 through the area between the collector and the emitter of a TR28. Then the juncture between emitters of TR131 and 141 is connected to the source 151 through the area between the collector and the emitter of a TR29. Thus a bias current Ie is varied by applying the control voltage between terminals 30a and 30b led out of the bases of TR28 and 28' as well as the base of the TR29. Then a time constant tau is changed and the phase is turned. |
