This circuit uses an LED (called SSL) to regulate current in a configuration with complementary transistors. The circuit is from 1970 General Electric documentation.
For analog lines, this circuit was found in the August 1994 issue of Electronics Now magazine. The...
This low-noise hydrophone circuit was found in a 1980s Linear Technology component manual. The...
This circuit is from an Electronic Design of the 90's. The circuit can be implemented with more...