Found in a 1968 EEE, this circuit accepts frequencies from 1 to 1000 Hz and control voltages from 0.1 to 15 V. The operational amplifier is from the era and can be replaced by modern equivalents.
This circuit generates frequencies determined by R3 and C1. We found it in the Radio Electronics magazine...
The configuration below is suggested by the National Semiconductor Linear Applications Handbook. The...
This charger circuit provides an initial voltage of 2.5 V and when the current reaches 180 mA the...