Found in a 1992 book, this circuit is intended for operation with audio signals. Equivalent operational amplifiers can be used. The optical coupler is an unusual type today.
Featuring an 8 MHz passband, Texas Instruments TVS912A operational amplifiers can be found at...
Suggested by General Electric in a 1967 publication, this circuit uses the D13T1, an uncommon SCR...
This hearing aid or stethoscope headset amplifier was found in a 1980s documentation. The...