Swend
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Why not use fix 1M & 1k and trim them for best CMRR...
and adjust the gain or "differential mode input voltage range" simply with R4?
Hi,
you want three different setups / ranges.
Can you tell me for each setup
* common mode voltage range
* differential mode voltage range
.. at the probe input.
Klaus
[FONT=Courier New]
R2/R3 C3/C4 DMpp CMpp
1M 0.016p 4800V 15000V
100K 0.16p 480V 1500V
10K 1.6p 48V 150V[/FONT]
No. It´s just internally compensated to enable gain down to unity.AD8130 is optimized for unity gain
Hi,
No. It´s just internally compensated to enable gain down to unity.
But for sure with increasing gain.... bandwidth will be reduced.
***
...then yes, setting the gain with the feedback will not give the expected performance.
Klaus
Max DMpp | Max CMpp | |
100K/1100p | 0-48V | 144V |
10K/100p | 48-480V | 1440V |
1K/10p | 480V-4800V | 14400V |
Every topology has pros and cons but my suggestion is that you don't implement ranges by changing R6/R9. See how I drew the schematic a few posts ago. The 10K and 2K are always in circuit. The switch selects which node goes into the amplifier.
Then by placing your dominant filter caps right after the 1meg resistor you'll have equal bandwidth for all ranges.
When it comes to matching look at resistor and capacitor networks. Search "ACAS", LT5400, and "X2Y" on digikey to see what I'm talking about. You'll need to calibrate the 1meg's buy maybe not other R's and C's if you choose these networks carefully.
Nice trick to see the frequency response in the time domain but I suggest you take a look at LTSpice's AC simulation ability at this point...
I'm wondering how there is a difference in gain flatness. Did you change the input amplitude to make sure you tested both ranges at the same nominal output amplitude?
Maybe the simulated input parasitic s of the amplifier are doing it. If so adding an impedance matching resistor between the 1k's and the amplifier input of 8k should match it to the 9k range.
Pintek DP-15K is rated 35MHz and 15kVpp differential, and 7.5kV common-mode, 100mV 50MEG input. From 15kV down to 1kV at 30MHz.
It uses two THS4631 for their I/P stage op-amps 325MHz FET input. Many compensation capacitors.
Maybe look at their probes to confirm what your requirements are for this project.
Your Spice sim has oddball huge capacitors to GND 192nF on the input circuit, I would not expect it to work at high frequencies.
I don't recognize a differential probe circuit. Previous post #76 looks better.
You have insufficient PCB clearance and the range switch is hardly suited for claimed 2kV. The usual solution found with the differential probes quoted in this thread (Pintek, Testec) is not to switch the top side of the voltage divider.
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