This circuit is from a 1965 Electronic Design. The transistors may be general purpose and the power supply must be symmetrical.
This is the traditional configuration of a high-pass filter with an operational amplifier, such as...
This circuit for incandescent lamps was found in the January 1980 Radio Elecronics magazine. The...
This amplifier was found in a 1969 Mullard documentation. The circuit uses transistors that have as...