>-----Original Message----- >From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] >Sent: 25 July 2005 18:47 >To: Microcontroller discussion list - Public. >Subject: [PIC]: Re: output source/sink characteristics > > >On 7/25/05, Bob Blick wrote: >> Here's something interesting I discovered while doing some >testing on >> a 16F876. I had RB7 output a high(to test the P-channel mosfet) and >> RB6 output a low(to test the N-channel mosfet), and put a series of >> three different loads between them, and after measuring the >voltages, >> calculated the equivalent on-resistances. >> >> The N-channel mosfet has lower resistance than the P-channel, of >> course. But they also behave differently. At higher loads the >> N-channel resistance stays pretty much the same. But the P-channel >> resistance increases noticeably with load. > > Not only with the load but also with the supply voltage. I've >made some tests on internal pull-up resistor (basically some P-channel >mosfet) values as a function of supply voltage ( between 2V >and 6V ). It's a disaster. > >best regards, >Vasile That would be the expected, normal behaviour. Lowering the supply voltage with a P-channel device reduces the applied Vgs and increases the resistance. Regards Mike ======================================================================= This e-mail is intended for the person it is addressed to only. The information contained in it may be confidential and/or protected by law. If you are not the intended recipient of this message, you must not make any use of this information, or copy or show it to any person. Please contact us immediately to tell us that you have received this e-mail, and return the original to us. Any use, forwarding, printing or copying of this message is strictly prohibited. No part of this message can be considered a request for goods or services. ======================================================================= -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist