Using an operational amplifier, this circuit from a 90s Popular Electronics, is characterized by its high sensitivity. R5 can be added to control the gain.
From an old manual of unijunction transistors, this oscillator generates different tones when the...
A negative floating regulator capable of supplying an output voltage of -100 V with regulation of 20 mV for...
Found in a Hands On Electronics of the 80s, this circuit makes use of a gas sensor of the time....