Found in a 1967 American publication, this circuit with feedback for two transistors has a gain of 20 times. Phototransistors are types of the time.
In this amplifier, the supply voltage is 35 V and the input resistance is 2k2. Equivalent...
This high speed laser diode driver was found in a 1980s documentation. Power FETs can be replaced...
This instrumentation amplifier with differential inputs was found in documentation from the 90s....