Peter, You can take an enhancement power MOSFET and put in the negative return line from your circuit. The gate is driven through a 1 Meg resistor from the positive supply terminal. A correct power connection drives the MOSFET fully ON, and everything works. Reversing the supply connections turns the MOSFET OFF, and no current flows and you're protected. Correct the power connections, and you're back to normal. There is very little voltage drop across the MOSFET. Select a MOSFET with a low "R(on)" resistance, and there will be very little voltage drop. David ----- Original Message ----- From: Peter Homann To: Sent: Sunday, May 30, 1999 5:20 PM Subject: Reverse Polarity Protection for 3V PIC Circuit. > Hi, > > I need to protect my PIC16LF84 against reverse polarity. Currently I'm > running the circuit of 2 x 1.5 N cells (2/3 AAA). I want to protect the > circuitry from the batteries being inserted the wrong way. > > I'm not keen to put a diode in series with the batteries as I'll loose 0.6V. > > Thanks, > > Peter. > --- > Peter Homann Email: peterh@adacel.com.au > Adacel Technologies Ltd _/_/_/ _/_/_/ _/ Phone: +61 3 9596 2991 > 250 Bay St, Brighton _/ _/ _/ _/ Fax: +61 3 9596 2960 > Victoria 3186 _/_/_/ _/ _/ Home: +61 3 9555 5603 > AUSTRALIA _/ _/ _/ _/_/_/Mobile: 0414-494578 > ------------------------------------------------------------------------ >