Re: gEDA-user: TO-92 Best Practices

[Peter TB Brett <peter@xxxxxxxxxxxxx>]

On Mon, 1 Mar 2010 22:50:29 -0800, Donald Tillman <don@xxxxxxxx> wrote:

> This particular project uses some analog IC design styles implemented  
> with hand-matched discrete transistors; diff amps, current mirrors and  
> so forth.  So I'd need an efficient way to hand-match surface mount  
> transistors.  With TO-92's I can just slap them into a rig and collect  
> them into batches.  Surface mount?  I dunno.  Do they even make SOT-23  
> sockets?

The usual approach is to buy SMT packages containing 2 or 4 transistors on
a single piece of silicon (i.e. literally back-to-back on the wafer).
They're invariably well-matched enough for all but the most ultra-precise
applications, in my experience.

These devices are used in designs for mass production, where manually
matching the transistors wouldn't be practical.

Peter

-- 
Peter Brett <peter@xxxxxxxxxxxxx>
Remote Sensing Research Group
Surrey Space Centre


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