LOG112: Vo3 max capacitive load

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:

hikaru_log112.TSC

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:

https://training.ti.com/ti-precision-labs-op-amps-stability-measuring-system-stability?context=1139747-1139745-14685-1138805-13851

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