This circuit provides reverse power polarity protection using a power MOSFET and a diode. The MOSFET must be current in accordance with the current of the protected circuit.
The circuit shown is from the Texas Instruments optoelectronics manual, applying to low power...
This circuit was found in a 1968 General Electric documentation. It has an input impedance of 2 M ohms...
This filter that rejects a frequency range determined by the double-T was found in the August 1993...