PWM applications

1-36 — elektor january 1980 ejektor an invitation to investigate, improve and implement imperfect but interesting ideas There are several possible applications for the self-oscillating PWM system described in Elektor 53, September 1979. Two interesting examples are discussed in this article: an interference suppressor and a multi-channel volume control. The interference suppressor (a sort of "spike trap, really) is extremely effective; the volume control has the advantage of good tracking between almost any number of channels. pulse is blocked. So is the signal, of course (figure 2a); but low-pass filtering at the output will clean it up again (figure 2b) — basically, this is the same principle as sampling. A better way of filling the "hole" where the spike was is to keep the signal level constant for the duration of the spike. This could be done by using a sample-and-hold circuit in the signal path, and arrange for the sampling pulses to be interrupted briefly when an interfe...