Using a MAX644 this circuit was found in the April 1989 issue of Radio Electronics magazine. The circuit is for a 5 V voltage and 50 mA current output.
The basis of this circuit is the HA2400 released at the time. The circuit is from a Radio...
This circuit with TTL output was found in a 1968 EEE. The transistor can be of general use. The...
This circuit can be found in a 1970 Motorola documentation. The circuit can be implemented with general...