Using red LEDs with ignition voltages of the order of 1.5 V we can make a multiple voltage reference. Current is low.
This op amp circuit is based on a 555 IC and two common op amps. Transistors are general purpose....
This circuit uses as a sensor a thermocouple to detect air flow. We found this circuit in a 1980s...
In the bridged configuration the TDA2002 amplifier can supply 30 W of power at a load of 4 ohms...