The diagram shows how the inexpensive and widely available 4066 quad bilateral analogue switch can be used to build a pulse generator with adjustable ‘high’ and ‘low’ times of the output waveform.
Assuming that switch IC-1a is open, the control input of IC-1b is logic high, and this switch is therefore closed. This results in low levels at the control inputs of IC-1c, and IC-1d. Capacitor C2 is charged via preset P1 and C3 via preset P2. When the voltage across C2 reaches a certain level, IC-1a is closed so that the control input of IC-1b is pulled low. The outputs of the circuit, 1 and 2 are then logic high. 1 has a swing o 5V and 2 a swing virtually equal to the supply voltage (max. 15 V).
Pulse Generator with One 4066 Circuit Diagram:
Meanwhile, switch IC-1c is closed, so that C2 is discharged. Switch IC-1a is opened, and C3 is charged via P2. When the voltage across C3 has reached a certain level, is closed, and the outputs of the circuit change to logic low.
The ‘low’ and ‘high’ times of the output waveform are adjusted with P1 and P2 respectively. With the component values specified, the ‘low’ time can be set between 136 µs and 3.75 ms and the ‘high’ time between 15 µs and 330 µs. Other ON and OFF times can be created by changing C2 and C3.
The circuit draws a current of about 8 mA at a supply voltage of 10 V. Note that 1 produces a less than perfect waveform, and has a low fan-out. The other output, 2, is buffered and should be used for most applications.