Precision Electronic Switching with Feedback Amplifiers

Abstract

Electronic-switching signal transmission devices have been, until recently, used principally for the simultaneous display of more than one waveform on a cathode ray oscillograph. During the past few years, however, in the field of electronic analog computers, several applications have required the development of electronic switches which have transmission characteristics consistent with the performance of precision computing elements. These precision switches utilize highly stabilized feedback amplifiers with the switching elements included in the forward gain portion of the loop to minimize the nonlinear characteristic effects. Multiple output switches, which provide either current or voltage output signal transmission from a single input voltage source, are available. Precision electronic time-division multipliers have been developed which utilize both current and voltage type switching circuits. Modulators and demodulators, utilizing voltage type switched-feedback amplifiers, have been developed with a linearity of 0.1 per cent. A multiple input switch has also been developed which involves an unusual circuit design. This design incorporates two separate input stages and a common output stage with separate feedback paths provided between the common output and the two inputs. With a square wave keying voltage alternately activating the two input stages, signals applied to the two input stages can be alternately connected to the output. The transmission stability and precision are largely dependent on the feedback loop gain of the amplifier and the switching speed on the amplifier bandwidth.