[sdiy] transistor matching circuit

[Peter Grenader]

As lame as this definition may be, a curve tracer plots the voltage/current
curve of anything plugged into it's test socket.  It usually involves with
it a scope in the X/Y mode, but many have built in tubes of their own.
Depending on the tracer's sophistication, one can arrange the DUT (device
under test) to a plethora of load configurations giving way  to 'see' many
different parametric specs on the tube.

For instance, if you put  5 volt zener in there and raise the test voltage
slowly you'll see basically a straight line which will elbow sharply at
somewhere around 5.1 volts indicating it's breakdown voltage.  While one
would not need a tracer to test a diode's limit, there are many parameters
that these things will come in handy for - transistor beta being one of
those as it's not linear.

We use to use them to sample test diodes and trannies at incoming
inspection, which the guys there hated doing because there was no handler
nor automated test involved.  You 'd have to set the machine up, insert the
correct adaptor and basically test them one at a time by hand, inserting and
reinserting and raising the voltage for each then making a visual
determination if the thing was to spec or not - their hesitancy was
understandable.

They are way cool machines though.

- P

Tom Arnold wrote:

> On Tue, Dec 14, 2004 at 03:17:26PM -0800, Peter Grenader wrote:
>> There a few of curve tracer scope fixtures on ebay right now going pretty
>> cheaply - under $50. The full blown tek's with the tube displays are still
>> pricey at about $500
> 
> Pardon me for being dense, but what exactly is a curve tracer?
> I see them surplus all the time for cheap but never paid much attention to
> them.