A Frequency Divider

Author: J.B. Hoag

In the circuit of Fig. 30 L, a rapid succession of square pulses is sent in at the left and a slow succession of square pulses is given out at the right.

Fig. 30 L. A frequency divider. (See R.C.A. Rev., p. 57, July 1940)

The output pulse rate is a definite sub-multiple of the input rate. The operation of the circuit is as follows: Negative halves of the input pulses are shunted to ground by the diode 1. Positive pulses pass through diode 2 into condenser C. The trigger tube is biased well below cutoff. When a sufficient number of positive pulses have entered C to raise the potential of the trigger tube to cutoff, its plate current starts to flow. This causes the multivibrator to produce one pulse. The number of pulses which had to be sent into C to cause this one pulse is the frequency-division-number. Note that the second grids of the multivibrator serve as the usual plates and that the actual plates are used, one for the output circuit, the other to pass electrons back to C to neutralize its charge and restore the initial conditions.