Author Topic: DIY 100MHz differential probe  (Read 9103 times)

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Online Berni

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Re: DIY 100MHz differential probe
« Reply #25 on: July 30, 2016, 06:41:18 am »
Wow I had no idea specialized opamps could be as easy to blow as simply feeding a high speed clock in to its input.
 

Offline mrpackethead

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Re: DIY 100MHz differential probe
« Reply #26 on: July 30, 2016, 06:50:31 am »
i reviewed THS3062, its not suitable for repetitive full swing signal application like this. anybody who wish to replicate this circuit may replace THS3062 with THS3092. fwiw.
Why so?
because i burnt 2 of them already... from the datasheet...


Is it pretty much a straight swap out?
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Offline Someone

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Re: DIY 100MHz differential probe
« Reply #27 on: July 30, 2016, 07:12:46 am »
That would require a sustained 100MHz input continuously at the majority of the working range, it doesn't seem to be a problem for realistic use of the probe. Many probes are derated for continuous HF signals.
 

Offline Mechatrommer

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Re: DIY 100MHz differential probe
« Reply #28 on: July 30, 2016, 09:57:22 am »
Wow I had no idea specialized opamps could be as easy to blow as simply feeding a high speed clock in to its input.
yup those current feedback opamps are very good water heater at normal operation. even the THS3092 and THS3096 mentioned above that is rated for repetitive signal will get hot. regardless non-repetitive or repetitive applications, they all need an aluminum heatsink on top, or else a very good solder contact at the bottom pad. the non-repetitive THS3062 will burn without smoke if you violate the above rule.

Is it pretty much a straight swap out?
you mean replacement? no, not straight if you want match freq respond, but workable and close enough. its just that the THS3062 is not the right opamp for high slewrate repetitive signal. but they all are very close at specs such as input voltage offset, current bias and offset. ymmv.

That would require a sustained 100MHz input continuously at the majority of the working range.
it was for my 50MHz FG output ±10V. due to gain respond, those opamps roll off starting somewhere 20MHz iirc, or it maybe in the diff probe i designed back then, i cant seems to accurately tell which. the THS3062 burnt, replaced with THS3091 iirc until now working. i still have 3 THS3062, that i'm going to use in my tracking PSU that i current do (thats why it came to my attention), a bit overkill i think but... as they are not good for anything else anymore, i'm going to use them up first. i'm just giving you a precaution, ymmv.
« Last Edit: July 30, 2016, 10:01:00 am by Mechatrommer »
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