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| 150V opamp feedback resistor suggestions |
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| duak:
Others have pointed out that the feedback resistor is probably dissipating too much power to meet your stability requirements and have presented solutions. If all gain determining resistors for can be thermally coupled together, the TCs should cancel out. This is where a monolithic or hybrid network on one substrate could work very well. If this is a multichannel assembly, each channel's network should be thermally isolated from its neighbors. A left field idea would be to have another resistor in the low voltage part of the signal path that would dissipate a similar amount of power and be similarly affected and could compensate for the resistor under question. I can't think of a simple circuit that either doesn't use another op-amp or doesn't mess with the noise gain of the existing opamp. Not knowing what op-amp is used or what the actual circuit is, could the op-amp also be contributing to part of the drift? With a supply rail of at least 150 V, the output devices could be dissipating enough power to cause a significant thermal gradient in the die that may affect the input offset. |
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