Other Parts Discussed in Thread: TINA-TI
Hi,
I'd like to know max allowable capacitive load of VO3 output in LOG112.
WIll you help me to find out the max value?
Thank you.
Hikaru
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Hi Hikaru,
there's no simple answer. It depends on the set gain, the values of feedback resistors, the chosen phase lead capacitance and whether an isolation resistor is installed:
You can easily find out the maximum capacitive load with a TINA-TI simulation of transient response: The overshot should be under 22% indicating a phase margin of > 45°. Any higher overshot indicates instabilty:
Kai
Mondori-san,
The output op amp is basically a general purpose op amp with sufficient ac performance to support the LOG112 use, but not designed specifically to drive a high capacitance load. Kai provides a thorough assessment of the LOG112 output-C-load capability using simulation. His simulations show the op amp's capacitive load is limited to a couple hundred picofarads, and compensation becomes necessary if it is increased beyond that level.
If you let us know what capacitive load you are considering driving that would provide us more insight what the op amp needs are.
Regards, Thomas
Precision Amplifiers Applications Engineering
Hi Kai and Thomas,
Thank you for your detailed explanation about my question. I understand capative load of this IC should be up to a couple of houndreds pF.
Thank you very much.
Hikaru