This circuit was found in a Popular Electronics from the 90s. The circuit uses a general purpose JFET. The coils depend on the signal range that must be amplified.
This circuit was found in a 1974 publication. It provides a tone indication of the temperature sensed by...
This is a simple rheostat circuit for motor control that works with voltages from 6 to 12 V. The...
This circuit with TTL compatible output was found in a 1968 US documentation. The circuit is...