Posted on Feb 7, 2014

Timing interval is initiated by applying power, and is determined by RT-CT. At end of interval, unijunction transistor triggers silicon controlled rectifier, to apply essentially full supply voltage to load. Delay range is from 0. 4millisec to 1 minute. - Transistor Manual, Seventh Edition, General Electric Co. 1964, p 321. (View) Addition of silico

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n unijunction transistor Q3 to conventional mono stable mvbr expands time delay two orders of magnitude. -M. P. Humblet, Unijunction Transistor Multiplies Monostable `s Pulsewidth, Electronics, 35:26, p 74-75. (View) This simple circuit acts as a frequency multiplier, which converts any sloped input waveform into a distorted output waveform, whose frequency spectrum is marked by a rich harmonics content. The input frequency does not disappear from the spectrum, however. When a pure sine-wave input signal is applied, the circuit generates odd harmonics only. The push-pull outputs of comparators IC1b and IC1a then supply differential signals to adder IC2, which cancels out even-numbered harmonics. For different mark/space ratios of the output signals, as set with P1 and P2, the harmonic spectrum changes. A duty factor of 0. 25, for instance, will cause the circuit to supply the second, sixth, and tenth harmonics, but not the fourth one. The spectrum function is then written as sin x/x. The reference levels for the input comparators determine the output waveform. The desired degree of distortion of the input waveform is, therefore, adjusted with the two presets. R2 and R3 should be matched to within 1 percent. (View) Feedback from collector to base of power transistor through C1 and R2 protects device from destructive transients generated when inductive load such as solenoid is turned off. Alternative use of diode CR2 or...

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