In this charger the current is limited by the incandescent lamp. Lamps from 40 to 100 W can be used and even connected in parallel, depending on the load.
The operational amplifier of this balanced circuit is old and can, however, be implemented with...
This SSB modulator does not use the balancer transformer. The circuit is from an 80's...
In the figure we show a configuration for a crystal controlled overtone oscillator using a...