EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: roadrunner777 on October 12, 2022, 03:59:22 am
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I have a signal generator, and an oscilloscope. I hook them up in parallel, I see the signal from the generator just fine. It's a 5V pulse, it's picture perfect on the scope.
I add an inductor in parallel to everything, and the waveform does what the books say an inductor should do. Again, perfect, just as expected.
Now, here is the thing: I would really like to have the scope show the source from the signal generator without the influence of the inductor on channel 1, and show the inductor doing it's thing on channel 2.
I have tried any number of transistor switch circuits to try and isolate the two, to see the signal source on one channel and the inductor on the other. But it's just been trial and error. Some invert. None of them show the same voltage exactly, the output with or without the inductor is always a little lower than the source voltage.
I think I need some kind of splitter maybe.
I have built about a dozen circuits trying to solve this, uncountable internet searches. Any help would be greatly appreciated. I have a fair stock of common transistors on hand.
Another little wrinkle... this may be a different thing entirely, but eventually I will want to do the same thing with RF.
Ok, thanks for any comments!
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I have a signal generator, and an oscilloscope. I hook them up in parallel, I see the signal from the generator just fine. It's a 5V pulse, it's picture perfect on the scope.
I add an inductor in parallel to everything, and the waveform does what the books say an inductor should do. Again, perfect, just as expected.
Now, here is the thing: I would really like to have the scope show the source from the signal generator without the influence of the inductor on channel 1, and show the inductor doing it's thing on channel 2.
I have tried any number of transistor switch circuits to try and isolate the two, to see the signal source on one channel and the inductor on the other. But it's just been trial and error. Some invert. None of them show the same voltage exactly, the output with or without the inductor is always a little lower than the source voltage.
I think I need some kind of splitter maybe.
I have built about a dozen circuits trying to solve this, uncountable internet searches. Any help would be greatly appreciated. I have a fair stock of common transistors on hand.
Another little wrinkle... this may be a different thing entirely, but eventually I will want to do the same thing with RF.
Ok, thanks for any comments!
In a word, "Buffer".
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Google has a bunch of videos re: 'inductor scope'. Among others:
https://www.youtube.com/watch?v=mg0cAUWUzG4&ab_channel=AleksZosuls (https://www.youtube.com/watch?v=mg0cAUWUzG4&ab_channel=AleksZosuls)
There are other videos in the series. https://www.youtube.com/channel/UC3s6t0UwccE_Bj_CNUEmB8A (https://www.youtube.com/channel/UC3s6t0UwccE_Bj_CNUEmB8A)
You will notice that these videos show a resistor in series with the inductor. Just like the RC circuit...
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Yes, the word 'buffer' is exactly what I needed. It looks like I am going to dive into op-amps a little earlier than intended... should be fun! Thank you.
And, thank you for the lead on the videos as well.
You know... when I first learned electronics, it was so long ago, we used slide rules. This is like starting all over again in some ways!
We can call this SOLVED. I don't know if there is a protocol for that on this forum. But I'm good to go!
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You won't have to dive in very far, a unity gain buffer with an op amp is pretty trivial to wire up. If you use a dual op-amp IC and make two buffers fed from the same input you'll have to isolated outputs.
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An "emitter follower" is a unity gain stage, a buffer. A very cheap solution.
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Here is an explanation of the emitter follower:
https://www.youtube.com/watch?v=8f-nhjQ1jMk&ab_channel=w2aew (https://www.youtube.com/watch?v=8f-nhjQ1jMk&ab_channel=w2aew)
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Thanks, I'm getting around to the videos now. Looks interesting.
I did build an op-amp based buffer around an AD847. I'm still tuning it... good results though. I stupidly bought the wrong bypass capacitors, waiting on new ones. I miss Radio Shack!
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Hey thanks!
Haven't thought about this for just basic play!
just looked at the vid, now i've added
Aleks Zosuls channel to my bookmarks
I like the idea of playing around with Op amps in the same way!