| Electronics > Projects, Designs, and Technical Stuff |
| Charge Amplifier - Spice vs. App Note |
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| sdouble:
--- Quote from: geo_leeman on April 24, 2019, 11:10:54 pm --- --- Quote from: sdouble on April 24, 2019, 08:38:28 pm ---your Cc is far too high. i should be in the (tens to hundreds of) pF range --- End quote --- Actually assuming Cc to be zero, the other cap is the sensor/transducer capacitance. --- End quote --- yep, my bad. Are you sure that it is of 20 uF ? That seems rather high. |
| geo_leeman:
In this case it is, just was working with some "nice" values for simulation. Real sensor is a plate about 10" in diameter. |
| sdouble:
a plate is not capacitive. are there 2 parallel plates ? |
| Zero999:
--- Quote from: geo_leeman on April 22, 2019, 03:10:27 am --- I made up a quick spreadsheet and modeled the circuit in LTSpice (granted, with a different opamp, but with high GBP and FET input) and my numbers don't quite agree. --- End quote --- For future reference, use LTSpice's UniversalOpamp model and set the gain, roll-off, input impedances to the same as the real op-amp you intend to use. It's not perfect, but better than using a random op-amp model, substantially different to the op-amp you're going to use. |
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