A pulse generator with a variable duty cycle can be easily constructed with only two ICs. This generator is composed of a clock circuit and a decimal divider.
The output of the decimal counter can be selected through a rotary switch. The diagram shows the outputs with different duty cycles. The circuit has two final outputs:
A and -A(minus A).
The table shows the percentage of the duty cycle at each output. The clock frequency can be varied through potentiometer P1. If several frequency ranges are desired and you
want to be able to change quickly from one range to another, connect several capacitors (for C') through a rotary switch. The capacitors' values are given in the table.
Electronic Circuits volume 1.0 - Circuit Nr. 82
The complete data of the electronic circuit described above can be found in the following book and is available from Amazon.com.
Click on the image to view the book.