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How do you measure bias with no source resistors?
How do you measure bias with no source resistors?
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Old 14th November 2019, 02:10 AM   #11
woody is offline woody
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What's up with r 25,26,27 & 28 ? It looks like you have them shorted out ?
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Old 14th November 2019, 11:28 AM   #12
JeffYoung is offline JeffYoung  Ireland
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How do you measure bias with no source resistors?
@woody, no, it's just poorly drawn because I never cleaned it up after playing with a few different ideas. The resistors are in parallel.

(I've also discovered that I can't find any metal films in 4W either, so they need doubling up again -- at which point there's not much point in showing them that way in SPICE.)

Here's a clearer version:

How do you measure bias with no source resistors?-jamjar-jpg
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Old 14th November 2019, 12:40 PM   #13
JeffYoung is offline JeffYoung  Ireland
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How do you measure bias with no source resistors?
Quote:
Originally Posted by Mark Johnson View Post
Consider the Hantek CC65 from eBay. I have one and I am pleased with the results I get from it.
I can certainly imagine other instances where being able to view the waveform would be very useful (such as determining the class A envelope -- assuming the output devices are on flying leads).

I did some Googling and Pico also sells one[1]. Looks like it was made in the same factory, but with slightly higher-spec parts (at least there's a strain relief on the cable, and a metal latch ring on the BNC). A bit more dosh, but maybe better quality control too?

Thanks for the idea, Mark!

Cheers,
Jeff.

[1] https://ie.farnell.com/pico-technolo...ope/dp/2677035
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Old 14th November 2019, 01:27 PM   #14
indra1 is offline indra1  Indonesia
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I'm not so sure on the how but new current clamps such as HoldPeak HP-870K shows DC current range.
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Old 14th November 2019, 02:48 PM   #15
Mark Johnson is offline Mark Johnson  United States
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How do you measure bias with no source resistors?
Here's another use I found for the cheapo Hantek current probe: visualizing and measuring inrush current when the AC mains is switched on.

_
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Old 14th November 2019, 03:27 PM   #16
woofertester is online now woofertester  United States
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DC current transformer.



Click the image to open in full size.
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Old 14th November 2019, 03:55 PM   #17
synonymous is offline synonymous  United States
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Voltage drop across Q11?
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Old 14th November 2019, 04:59 PM   #18
JeffYoung is offline JeffYoung  Ireland
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How do you measure bias with no source resistors?
To do it based on voltage drop across Q11 wouldn't you need to know what the transfer curve looked like at the rail voltage? (The datasheet only contains curves at 10Vds.)
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Old 14th November 2019, 06:40 PM   #19
Nelson Pass is offline Nelson Pass  United States
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How do you measure bias with no source resistors?
I just put a .1 ohm resistor in series with each Drain/Collector. Works fine.
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Old 14th November 2019, 09:27 PM   #20
GKTAUDIO is offline GKTAUDIO  United States
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