[sdiy] Re: Modern transistor matching

[Bruce Duncan]

At 09:19 PM 3/20/2008, you wrote:

>>The Dual 3904s seem to be quite well matched and the low mass of
>>both the transistors and 0805 T. resistor
>>means they will probably remain very close to the boards temperature.
>
>The last bag of 100 x 2N3904 transistors I got from Mouser, I sorted
>them by my usual method.
>
>All 100 tested +/- 1 mv. of each other at room temperature (all 100
>came out of bag matched to each other to Moog spec.)
>
>Either I lucked out and got a chance pull from a single process bin,
>or process control is getting good enough to control semiconductor
>doping down to the molecular level.
>
>I couldn't believe it so I checked some with different equipment,
>same result.
>
>I have also noticed that a bag of 200 x 5% resistors also seem to
>match to 1% or better within the same bag (to each other but not to
>spec'ed value).
>
>I used to have to do all that X-bar chart process control stuff, it
>seems like SOME processes are quite under control today.


I have noticed this too.
We just matched up a 100 or so 2N3904s with the same result.
And I bought a thousand of them for like 20 bucks.
They also came from Mouser.


Bruce