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| Nulling Input Offset Voltage |
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| David Hess:
If you want to keep your existing high voltage amplifier then there are a couple of ways to DC stabilize it but for simplicity I would start with the non-inverting example shown in the Burr-Brown application note included below. Typically a precision part like an LT1001 or OP07 would be used but if you need single supply operation, then there are precision single supply parts like the LT1006/LT1013/LT1014. The idea is to enclose the high voltage output stage which is configured for a fixed gain inside the feedback loop of the precision operational amplifier. The output stage gain needs to be high enough so the precision amplifier can drive it. But there are some things to be aware of: 1. The high voltage at the output can get back through the feedback network and damage the precision operational amplifier so a clamp should be used. This is especially a problem if a feedback capacitor is used on the outer feedback network. 2. The added phase lag of the output amplifier can make the input amplifier unstable. Using a slow input amplifier or adding AC feedback between the input amplifier's output and inverting input solves this. |
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