Dear all,
I am triying to simulate the TIA behavior of OPA858 using TI-TINA. I'm tring to I have some questions below:
1. Since the OPA858 is the kind of decompsensated OA, can I directly use the value of GBW(5.5Ghz) to estimate the f-3dB using the formula below:
2. Snapshot of the TINA schematic below. I'm wondering if the sysytem is stable.
Thanks,
Joey
Hi Joey,
the minimum phase margin for stable operation is about 45°. Your circuit results in a phase margin of 44°:
You can improve the phase margin by shorting the 1k resistor at the +input of OPAmp or by paralleling a 10n cap:
A further improvement can be achieved by increasing the phase lead capacitance from 750f to 1p:
A higher bandwidth can only be achieved with a lower detector capacitance.
Kai
