At 10:58 AM 3/2/2004 -0700, you wrote: >>From: Spehro Pefhany >>>I have a circuit, that uses a voltage divider on a control pin, to turn it >>>on and off. Basically if the voltage is present, and above a 1.32V >>>threshold, then the controller is activated. I want to remotly control >>>this >>>device, so I tied a N channel FET (BSS138) where the source is tied to the >>>control pin, and the drain is tied to ground, and the gate has a 1K >>>pulldown >>>and then driven from a PIC. >> >>I think you've got drain and source reversed. The MOSFET will actually >>sort-of work in reverse, but the body diode is conducting and keeping >>the source voltage from going more than one diode drop above ground. > >Also, Spehro, I think I would have used a bigger pulldown, no? Sure, the only concerns would be speed and leakage current...if the output isn't going to be tristated, I don't see any need for a pulldown at all (maybe if the power can be removed from the PIC?, but then the protection diodes will pull the gate to a few hundred mV). 10K or 30K should be about as good, in any case. Maybe infinity. But 1K shouldn't stop it from working, in any case. Best regards, Spehro Pefhany --"it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads