Hello Declan, > I'm going to make a few wild guesses, seeing as you won't > tell us about what you want help with ;-). I won't try a second time because if > you want help, a basic minimum is that you tell us what you want help with!! > I'm guessing it's a cpu controlled design you're in the middle of,
Yes, it is a cpu controlled design, so far your guess is right. > system switched onto the same output - whichever one is appropiate. I gather you have a few digital i/o pins, and you want to power this variable voltage line from the program. Is any of that right? This guess is close, but not right. I already have a source available which can be switched between several voltages, but with too less current. It's the current which I want to boost and limit, at the appropriate voltage. With thanks to this list and the good old Horowitz and Hill, I now designed a circuit with an voltage follower and a NPN transistor at the output, taking care of the current boost. I added a PNP transistor with some resistors and two diodes as a current limit switch. I simulated the circuit in Multisim and it seems to work (first spending half a day finding out that not all opamp models were complete :-( which resulted in a 7.7V output voltage out of a 5V feeded opamp, patent pending now of course ;-)). I use an available 12V supply voltage to feed the opamp and transistor circuit, leaving enough overhead for the current limiting resistor and output range of the opamp. If there's a solution which is much easier and cheaper, please let me know... Kind regards, Elbert. -- Author: Elbert Smit INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB CHIPDIR-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
