Wanting To Build A Transistor Curve Tracer To Use With My Oscilloscope

dnpainting

dnpainting

Super Member
Well, like the title says, I was looking into building a transistor curve tracer to use with my oscilloscope and came across this design. http://www.intio.or.jp/jf10zl/trct.htm

I wanted to get your opinion if you could be so kind as to look at it, post any suggestions or changes you would make if you were going to build this.

I did have a couple questions about this schematic. Probably stupid questions but here it goes. Coming off the 7490 IC is listed as having 3 silicon shottoky barrier diodes, but no number is there. Are those just part of the IC? If not, can you suggest ones that would work?

Reason for building: I thought this would be an interesting build other than this type of curve tracer: http://www.techlib.com/electronics/curvetrace.html
Plus, I have all the parts, except the shottoky's and I'm a cheapy and can't afford a real curve tracer.

Thanks for your help!

David
 
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The diodes are not part of the IC. But they are not all that critical either. They are just acting as a switch with low on (forward) voltage. Any low current schottky should work fine.
The circuit is simple, but should work fine if you don't need a high degree of precision.

Terry
 
Curve tracers are cool and all, but when we had the use of one the most used feature was PRV/PIV (Peak Inverse/Peak Reverse Voltage), for VCEo . Usually, the basic one's don't have that function. A good DMM, that you're used to, will give you most of what a curve tracer can give you in terms of testing transistors. On very rare occasions, a curve tracer can show you lower voltage breakdown or leaky paths.

If it only supports lower voltage testing, I would try to put in an A/B switch so that two samples could be compared for things like gain. Comes in handy for matching. You can probably measure many zeners too.

Calibration. There should be some way of calibrating the Curve Tracer. Without calibration, the divisions on the scope don't mean very much.



Hmmmm, ......... 5V is all its got?? Kind of approaching "toy" category. I have a Leader curve tracer somewhere. I think it has the schematic too. Do you want to take a look at that?
 
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The old B&K 501A goes up to 100V on the collector supply, which makes it useful for finding devices with low breakdown voltage. I suspect this item comes up for sale frequently on that auction site.
 
It looks like the one in the first link "sweeps" Vc from 0 to 16V and steps Ib (0 - 20 - 40 - 60 - 80 uA) to give a "family" of curves.
The A-B switch is a great idea.
 
Thank you Jon searching and for the link for the Leader CT.

While in search of different Ideas on what to build as far as a curve tracer, I came upon these 2 sites for schematics of different test equipment:
http://www.nostalgickitscentral.com/eico/products/eico_test.html

and

http://web.archive.org/web/20020201194744/http://www.circuitarchive.co.uk/heath.htm

Wanted to post here in case someone is in need of a manual or schematic sometime!

BinaryMike said:
The old B&K 501A goes up to 100V on the collector supply, which makes it useful for finding devices with low breakdown voltage. I suspect this item comes up for sale frequently on that auction site.
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I was trying to avoid purchasing if I could build one, as I have all these parts already.
I do have a B&K 650 Tube Tester that has a transistor test for leakage and gain. Would I be better off just using that than building the one I specified? Are these usually pretty accurate?

Thanks
 
dnpainting said:
I do have a B&K 650 Tube Tester that has a transistor test for leakage and gain. Would I be better off just using that than building the one I specified? Are these usually pretty accurate?
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I don't think I've ever used the transistor test function of a tube tester, although at least one of my tube testers sports that feature. I have used an old DC-only RCA portable transistor tester on many occasions, and I'm reasonably certain that its gain measurements agreed with the curve tracer at similar test currents. In the end, I finally put the monster Tek 575 curve tracer on a scope cart and equipped it with long test leads so I could use it routinely as a troubleshooting tool, because that seemed to be the only way of knowing for certain that a transistor is good or bad. Breakdown at lower than specified voltage is one of the sneaky problems that good curve tracers easily identify.
 
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BinaryMike said:
I don't think I've ever used the transistor test function of a tube tester, although at least one of my tube testers sports that feature. I have used an old DC-only RCA portable transistor tester on many occasions, and I'm reasonably certain that its gain measurements agreed with the curve tracer at similar test currents. In the end, I finally put the monster Tek 575 curve tracer on a scope cart and equipped it with long test leads so I could use it routinely as a troubleshooting tool, because that seemed to be the only way of knowing for certain that a transistor is good or bad. Breakdown at lower than specified voltage is one of the sneaky problems that good curve tracers easily identify.
Click to expand...

Thank you Mike. I will have to keep my eye out for one in my price range. I appreciate all the help.
 
I am in total agreement with Mike. A good curve tracer is very useful. I use my Tek 575 almost everyday. Look for a good second hand curve tracer.

Forget the toys on the first post.
 
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