Oscilloscope probe voltage derating vs frequency

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schmitt trigger

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What is the technical reason which the scope probes are derated with frequency?

This is a generic probe from TPI, but have seen the same behavior on other brands, too
 

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Current handling of the compensation caps?
 

Frequency limit is unusually low. Many passive probes have full voltage rating up to 1 MHz.

I'd expect that voltage divider HV resistor as well as HV capacitor have high frequency derating.
 

yes, current at 600Vrms at 1GHz in the probe's capacitance would be high - also almost all caps have to be derated with freq - due to losses in the dielectric and loss of volt withstand with freq
 

From Tektronix application note Oscilloscope Probe Circuits by Joe Weber:

Reverse termination is referring to series resistor R2 in the below schematic, cable I²R is significant because passive probes are using a lossy cable with resistance wire inner conductor.

 
Makes sense now!

I was wondering how come a 600VDC probe would only withstand about 50V @ 10 Mhz, which is not that high in frequency.

Fortunately, logic circuits running that fast are all low voltage.

But it could be a problem in some modern SMPS powertrains.
 

The more typical derating curves of modern 10:1 and 100:1 probes should be sufficient for most SMPS applications.

 

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