[sdiy] Transistor help

[Harry Bissell Jr]

You can get metal film tempcos from

http://www.micro-ohm.com/temperature/temprecflm.html

LPTC12 	1/6W  1000~3.9K ±2% to ±15% 	
LPTC25  1/4   1.0~3.0K	±2% to ±15% 

They usually stock the 1K +3500 5% value... they
are about $1 / 100 pcs.

Buy a bunch and share with your friends...  :^P

(I've used a bunch, they work quite well !)

H^) harry




--- Pete <23isgood at gmail.com> wrote:
> You can get tempco resistors from the site below but
> they are not
> inexpensive. I got a quote for $6.71 each and a 15
> piece minimum. I
> have not orderd any.
> 
> PT146 2000 ohm 1%
>             @25 C
>             TC 3500 ppm/degree C
> 15 pc.min.@$6.71 ea.
> 
> http://www.precisionresistor.com/
> 
> 
> On 4/26/05, René Schmitz <uzs159 at uni-bonn.de> wrote:
> > Hi Fiercefish,
> > 
> > Fiercefish wrote:
> > > Hi all, I have just bought a batch of 2n3904's
> for my soundlab
> > > minisynth project, I have a meter that can
> measure the hFE of them so
> > > will this allow me to select matched pairs by
> choosing those with the
> > > closest value? Also I apparently need to find
> some noisy 3904's for
> > > the noise generator, what sort of hFE reading
> (if any) would yield
> > > the most noise eg high or low? Sorry if these
> seem like dumb
> > > questions, I do not know if the hFE value is
> related to these factors
> > > but it is the only method I have of testing
> them, unless there is
> > > another way of course. I'd be greatful for any
> input or other
> > > suggestions, thanks.
> > 
> > hFE is not the right way to select matched pairs.
> You need to supply a
> > constant current through the collector, and you
> would measure the Vbe
> > that you need for that current. What I was always
> using is to put a
> > resistor from collector to V+ and from emitter to
> V- (with an assumed
> > +-15V and the resistors being 150k you get about
> 100uA.) The base is
> > grounded, and you read the voltage between base
> (GND) and emitter. Find
> > the ones that have the reading which most close
> together.
> > 
> > Cheers,
> >   René
> > 
> > --
> > uzs159 at uni-bonn.de
> > http://www.uni-bonn.de/~uzs159
> > 
> > 
> 
> 
> -- 
> listen to my latest tunes,
> 
> http://www.cubanpetemusic.com/p23%20Litmus.mp3
> 
> www.cubanpetemusic.com
> 
>