On Sat, 27 Nov 1999 21:01:55 -0800, you wrote:

>At 09:36 PM 11/27/99 +0800, you wrote:
>>Hi guys
>>
>>Got a big program hope you can help.
>>
>>Does anyone know of any circuit that is able to produce a constant
>>current(250mA) and voltage(about 5 to 10V).If you have it can you sent it to
>>me ASAP. thanks
>>
>>if you have any infor please mail to me
>
>Take a look at just about any data sheet for a 3-pin regulator--should be a
>circuit there for constant current.  All you need is the regulator and one
>resistor to set the current.  LM317's work fairly well and can handle the
>current.  You will lose about 1.25 volts across the resistor.  AND be sure
>to put a 1 uF cap across the resistor as well--really does wonders for
>current stability.  DO NOT put a cap from the output to ground, however.
>
>Kelly
>
>William K. Borsum, P.E. -- OEM Dataloggers and Instrumentation Systems
><borsum@dascor.com> & <www.dascor.com>San Diego, California, USA

Use an ordinary 7805 - it makes a regulated 5 volts, and if you put a
constant load across that, such as a lamp, then the regulator looks to
the outside world like a constant current regulator.  Great for battery
charging!

Peter