[sdiy] Transistor help

[Terry Ahrens]

I'm sorry, but I think this in error. 
The PT 146 is a 1K tempco resistor.  I recently purchased a batch of 10
of these from Precision Resistors, and they were (and are still) only $3.10
apiece. IIRC, the minimum order is $25 regardless of # of items.
Perhaps you were referring to different part#?


Pete <23isgood at gmail.com> on Tuesday, April 26, 2005 at 10:33 AM  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
>> 
>> 
>
>
>-- 
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>
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>
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