This circuit uses an HA2400 consisting of 4 digitally controlled operational amplifiers. The circuit is from a Radio Electronics magazine from March 1980. The power supply must be symmetrical.
This circuit uses two Raytheon RC4558 operational amplifiers that are similar to the 741. The...
This small stereo amplifier for headphones was found in a documentation on integrated circuits from...
This is a MOSFET version of a grid dip meter for frequencies between 1.8 MHz and 150 MHz,...