DIY Curve tracer needed - Page 1
Forum section: electronics / testgear

author: jeffjmr
author_rank: Regular Contributor
timestamp: March 18, 2022, 02:12:00 pm
content: Some time ago, when I didn’t really need one, I came across a DIY curve tracer circuit that worked with a wave generator and oscilloscope.Now I’d like one to match transistors and zeners and the only circuits I can find include a wave generator.Anyone have a schematic for one that you can provide your own wave input?Thanks,Jeff

author: ledtester
author_rank: Super Contributor
timestamp: March 18, 2022, 02:43:30 pm
content: You might be interested in this video:#197:Simple V-I curve tracer using an oscilloscope and function generator -- w2aewhttps://youtu.be/WWY-pakm_OMBasic idea:It's not perfect since the burden voltage of the current sense resistor is added to the voltage probe.

author: pqass
author_rank: Super Contributor
timestamp: March 18, 2022, 03:35:56 pm
content: Here's another:https://sound-au.com/project119.htmEDIT: Just found this version... from a w2aew video.You just need to invert the Y axis.

author: TERRA Operative
author_rank: Super Contributor
timestamp: March 18, 2022, 04:05:23 pm
content: Check out the 'octopus curve tracer' on the Googles. It's a simple curve tracer and Goole will give you much better info than I can summarise here.

author: Ian.M
author_rank: Super Contributor
timestamp: March 18, 2022, 04:16:38 pm
content: https://www.eevblog.com/forum/beginners/dirt-cheap-and-simple-scope-based-component-tester-curve-tracer/Lots of info and links to various curve tracer circuits. The one that caught my eye was the PC soundcard driven curve tracer by Dr George R. Steber, WB9LVI, which looks like it could meet your requirements, provided your scope can do waveform math to display Y1 and Y2-Y1 in X-Y mode, or of course it could be PC hosted as originally intended.

author: ledtester
author_rank: Super Contributor
timestamp: March 18, 2022, 04:26:42 pm
content: Perhaps the OP can elaborate on what he means by:Quote

author: jeffjmr
author_rank: Regular Contributor
timestamp: March 18, 2022, 07:28:27 pm
content: I have a Rigol MSO5472. It has two AWG channels, and I believe it can do the X-Y math.The DIY circuits I have found all have some sort of generator as part of the circuit and my limited knowledge prevents me from being able to proceed to build by simply eliminating the generator section.Also, the simple circuits graciously offered above look workable if only there were values of the transformers and other components, power supply required and the three BCE connection points shown. All regrettably above my experience level to discern on my own.I could buy one of the off-the-shelf component testers but every gizmo I build provides a much needed learning experience for me.Thanks all for your advice.Jeff

author: jeffjmr
author_rank: Regular Contributor
timestamp: March 18, 2022, 07:57:15 pm
content: Quote from: ledtester on March 18, 2022, 04:26:42 pmMy understanding is to adequately curve trace transistors requires a sawtooth input. My Rigol can provide that so I don’t need a circuit that provides a built-in wave generator.Jeff

author: John B
author_rank: Frequent Contributor
timestamp: March 19, 2022, 01:29:32 am
content: I built something basically along those lines. It's essentially a relatively low frequency class AB audio amp which used my scopes wave generator, then fed back a voltage and a current signal.Instead of the voltage input being replicated on the output, it was a transconductance amplifier which provided some safety against over-current situations on diodes, transistor bases etc where voltage source could easily burn them out.It had some weird phase shift and non linearities in the waveforms which I never got around to investigating fully.