This circuit with TTL output was found in a 1968 EEE. The transistor can be of general use. The tunnel diode is an uncommon component today.
A touch on the sensor causes the relay to trip and remain so, for a time that can be adjusted in...
Found in a 90s General Electric documentation, this circuit has a drain current of just 1.5 uA....
In the figure we have a differentiator with the LM3900 transconductance amplifier. The circuit is...