Pulse generator

Repeating Pulse Generator

The circuit uses one of the four bilateral switches contained in the CD4066, and is a kind of astable multi-vibrator. The main limitations of the circuit are the relatively poor shape of the output signal, and the output signal swing, which is not digitally compatible. These drawbacks are easily overcome, however, by a buffer at the output. When the switch closes, the current in the chain produces a voltage across R3, which raises the switching level at the trigger point by about one volt. Likewise, R1 reduces the voltage applied to R4 to a level below the switch-off voltage. The mark-to-space ratio (duty factor) of the output signal may be varied by using parallel charging resistors, one with a series diode (preferably a germanium type), as shown in the circuit diagram.

Pulse generator

In the prototype, the component values shown resulted in an output frequency of 957 Hz with a supply voltage exactly The duty factor was about 0.4 without the parallel RD network .With the network fitted, the output frequency and duty factor were 317 Hz and 0.06 respectively.

The current drain varied between 0.12 mA and 0.39 mA.

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