How to step down 1MHz 100Vpk signal ???

[LordAli]

Hello,
I have signal of 1MHz frequency and 100Vpk. I need to step it down from 100Vpk to 1Vpk, so 100:1 attenuation. It's not power signal, just feedback signal from winding.

I think there are few solutions:
1) capacitive divider (I would rather avoid it)
2) resistive-inductive divider
3) tapped inductor (my boss will probably protest against the solution with magnetic components)
4) 100:1 step-down transformer (same note as in 3)

What do you think what is good solution for industrial device? Is there another method how to step down so high voltage? Resistive divider is not applicable, because high upper resistance makes low-pass filter with parasitic capacitances high below the required measuring frequency.

thanks

 

[barry]

Can you supply 1 Watt? If so, then you could use a 10K/100ohm divider. For a cutoff of 1MHz, you'd need to have about 16pf of parasitic capacitance, which sounds like a lot to me. I would look for a way to minimize the parasitics and then use a resistive divider. If you can't minimize parasitics, you're stuck with either a reactive solution, or a way to compensate for the parasitics. If the parasitics are known, and the frequency is fixed, could you then just calibrate your measurement knowing that it's being attenuated by a filter?

Barry

 

[chuckey]

Depending on the capacitance of your low level circuit, put a capacitor of 1/100 th of its value across the top resistor. So cable /amplifier capacitance of your sample circuitry is say 80 pF,swamp this with a 220 pF capacitor, so if the 80 pF changes it will be a smaller fraction of the total. So you have 300 pF total capacity, put a 3 pF capacitor across the top resistor. Choose you resistors like Barry says 10k + 1k or 100k +1k, 1M +100k. .
Frank

 

[LordAli]

Thanks guys,
I'll try that. I'll try capacitor divider and probably some experiments with >10k resistor. Because I need also 1.6MHz signal to pass through. Moreover I need not to change signal phase, it will be done with proper cutoff frequency.

 

[mtwieg]

You can definitely do this with a resistive divider and a compensation capacitor. Heck, just use a 10:1 oscilloscope probe, or an equivalent circuit as a first stage.

 

[darkseid]

Hi

You can also use a ferrite core transformer rated for 1MHz frequency. You need the check the exact code of the ferrite material for 1MHz.