This light meter circuit was found in 80's Radio Electronics. The circuit uses a milliammeter as an indicator and the sensor is a common LDR. The power supply must be symmetrical.
This linear oscillator was found in a 1968 publication. The operational amplifier is from that...
This circuit was found in Radio Electronics from May 1965. The SCRs and transistors are from that...
This Wien bridge circuit, using a 741 operational amplifier, was suggested by Texas Instruments in its 1996...