基本信息
摘要：986,098. Semi-conductor demodulator circuits. GENERAL ELECTRIC CO. Ltd., and C. BOWDEN. April 13, 1961 [April 13, 1960], No. 13282/60. Heading H3T. A circuit arranged to produce a voltage across a capacitor in dependence upon the amplitude of an input signal comprises a transistor and a Zener diode connected in a D.C. path between the output circuit of the transistor and the capacitor. The input signal is applied to the transistor to control the current in the output circuit when the capacitor is discharging, the transistor being periodically cut off to charge the capacitor through the Zener diode in the reverse direction. The input signal is fed to a unit 2 which produces two quadrature outputs, the first of which has its positive-going portions removed and is fed through an amplifier 4 to the base of transistor 6 via resistor 9, and the second of which is fed to the shaper 3 which produces sharp positive-going pulses concident with the peaks of the negative-going signal. These pulses are of sufficient amplitude to cut off the transistor and are fed to the base via capacitor 5. During the time the transistor is cut off, the capacitor 15 charges through resistor 12 and Zener diode 14, during the remainder of the time period, the capacitor discharges through the transistor to a potential determined by current in the output circuit of the transistor, which is controlled by the input from amplifier 4. The resulting potential is smoothed and fed via emitter follower 19 to control the attenuation of attenuator 22 (see Specification 986,009) connected in a sweep oscillator signal path 25-32 of a vibration tester, the signal 1 being derived from an accelerometer mounted on the vibrator.
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