This circuit is from a Radio Electronics magazine from May 1986. Observe the voltages applied to the capacitors, taking care that the capacitor under test can withstand them.
This circuit uses an operational amplifier to simulate an inductor. The circuit is from old...
This voltage level-triggered circuit was found in a 1969 Ferranti English documentation. Modern...
Found in a 90s General Electric documentation, this circuit has a drain current of just 1.5 uA....