John Remington wrote: >at a suggestion of a coworker, I changed the resister on the 2N2222A's >collector to 1k, which changes the gain of that transistor. Now the fet's >Vds is 1v, looks much better. > Huh? Yes, it LOWERS the gain, but we are still talking about an on off situation. Where the collector goes from off to on and the cooresponding collector voltage is either .1V or 12 volts. The gate has NO loading to the collector, so gain should have no effect. >I'll try the P-channel fet, but I don't think I have any on hand. > >Thanks for the input If my mw is to high I'll be going to a different >device . . . maybe the P complement to an IRF510 or something . . . > >IRF9510 > > >On 4/21/06, Thomas C. Sefranek wrote: > > >>-----Original Message----- >>From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf >>Of >>Roy J. Gromlich - PA >>Sent: Friday, April 21, 2006 1:38 PM >>To: Microcontroller discussion list - Public. >>Subject: Re: [EE] JFET 2N7000 as SS Relays >> >>The Vds on the FET should be a whole lot less than 2.4 Volts at 37 mA - >>actually I would think more like 0,24 Volts. The 2N-7000 FETs have a >>nice low ON resistance when saturated - I would have to say that yours >>is not. >> >>RJG >> >>He is still using an FET source follower, as a high side switch, >>it will never saturate. >> >>Hint for John: For a high side switch use a P-Channel FET. >>Source to V+, same gate circuit, drain to the load. >>You can get some REAL low drop switches that way. >> >>Tom >> >> * >> | __O Thomas C. Sefranek tcs@cmcorp.com >> |_-\<,_ Amateur Radio Operator: WA1RHP >> (*)/ (*) Bicycle mobile on 145.41MHz PL74.4 >> >>ARRL Instructor, Technical Specialist, VE Contact. >>http://hamradio.cmcorp.com/inventory/Inventory.html >>http://www.harvardrepeater.org >> >> >>-- >>http://www.piclist.com PIC/SX FAQ & list archive >>View/change your membership options at >>http://mailman.mit.edu/mailman/listinfo/piclist >> >> >> -- * | __O Thomas C. Sefranek WA1RHP@ARRL.net |_-\<,_ Amateur Radio Operator: WA1RHP (*)/ (*) Bicycle mobile on 145.41, 448.625 MHz http://hamradio.cmcorp.com/inventory/Inventory.html http://www.harvardrepeater.org -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist