Curve Tracer Schematic

[BYacey]

I am looking to build a transistor curve tracer, something perhaps along the lines of the Eico 443. Does anybody have a schematic for this or a similar device? I would like to have a look at various designs and decide what best suits my purposes.
Thanks

 

[daArry]

Hey,

http://homepage.ntlworld.com/nausicaa.valley/INDEX.html

Peep Component Analyzers project...

 

[NewYorkDave]

Those "component analyzer" gadgets are handy--I built two similar devices for my own use when I was a bench tech. Although they do show a V-I curve, the term "curve tracer" is usually reserved for a more sophisticated device that provides stepped base/gate/grid drive among other features.

Here's somebody's marked-up copy of the Heathkit IT-3121 schematic

Somewhere, I have the manual for this as well as a curve tracer made by BK. Both the Heath and the BK display on an external scope. The king of the semiconductor curve tracers was the Tek 576, but I don't think you'll want to DIY one of those.

If you give some detail about your application, that'll make it easier to recommend something.

 

[BYacey]

Thanks for the replies. I want to be able to check power transistors with up to 300V rating, so I should have a PIV adjustment of up to 350V or so. As well I want to be able to compare transistors for matching gain between devices. Mostly power transistors.

This project is spurred on by the fact that I bought a bunch of counterfeit Motorola power transistors, MJ15025's. I must have spent an additional 10 hours trying to find why the outputs were failing in a power amp I was rebuilding. I want to test devices now before putting them into service.

 

[rafafredd]

[quote author="NewYorkDave"]copy of the Heathkit IT-3121 schematic[/quote]

For some reason I can´t see it...

 

[tk@halmi]

I have a CT-71 curve tracer for sale if interested.
gfargone_at_yahoo_dot_com

 

[NewYorkDave]

Bill, it sounds like you could use homemade jigs to run the tests you need. For breakdown voltage, you'd need a current-limited variable high voltage supply. For gain matching (AC or DC), a simple amplifier circuit in which you can easily vary the terminal voltages, and a voltmeter to measure the gain.

 

[bcarso]

"Bill, it sounds like you could use homemade jigs to run the tests you need. For breakdown voltage, you'd need a current-limited variable high voltage supply."

And to determine breakdown voltage, just a big value R in series with a high voltage supply is adequate, and in fact usually safer, since a lot of current-limited supplies have a large output capacitor and can thereby supply a large peak current before the limiting starts to work. The resistor won't have that problem, and you can just have a voltmeter set up before turning on the high voltage to observe the breakdown voltage.

Make sure to measure under relevant conditions, i.e. similar to the circuit the part will be used in---a comparable impedance in the base-emitter circuit.

 

[BYacey]

Yes I know I could build some jigs, but on the other hand I would like to build a complete self contained unit that I can use with the scope X-Y axis. This will keep my test gear from being tied up for such tasks and more convenient overall.