[sdiy] Transistor help

[Ray Wilson]

The Precision Resistor PT146 is spec'd for its tempco characteristics. The 
1K is the stock and therefore cheaper part. The 2Ks are special order and 
are more expensive than the 1K. I just ordered 100 pieces of the 2K and they 
were about $4.40 or so a piece in that quantity. They also have a four week 
lead time.

I plan to offer the tempco and a VCO board for $25.00 starting in May.

Cheers

Ray





----- Original Message ----- 
From: "Terry Ahrens" <tahrens at scoe.net>
To: "Pete" <23isgood at gmail.com>; <synth-diy at dropmix.xs4all.nl>
Sent: Wednesday, April 27, 2005 6:49 PM
Subject: Re: [sdiy] Transistor help


> 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
>>>
>>>
>>
>>
>>-- 
>>listen to my latest tunes,
>>
>>http://www.cubanpetemusic.com/p23%20Litmus.mp3
>>
>>www.cubanpetemusic.com
>>
>>
>>
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