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OPA2192: Op amp GBW recommendation

Naddy MY
Prodigy 20 points
Part Number: OPA320
Other Parts Discussed in Thread: OPA328, OPA828

Tool/software:

Hi, im looking for a suitable op amp to amplify my signal.

My input is 0.3mV and 2 MHz pulse.

I know one of the most important specs to look at is the GBW. 

I want to test on a stripboard, thus would prefer a non high speed op amp device.

If I have a target gain of 3.

So the GBW is 6MHz.

Is it possible to leave a safe margin of 5 (hence opt for 30MHz op amp) instead of 10 (that requires me to opt for a high speed op amp with GBW of 60).

I would also appreciate any recommendation for suitable op amp. I dont mind with the supply voltage as I have a dual supply voltage that could give up to +-25V. 

  • +1
    TI__Guru* 77091 points

    Hi Naddy, 

    Naddy MY said:
    Is it possible to leave a safe margin of 5 (hence opt for 30MHz op amp) instead of 10 (that requires me to opt for a high speed op amp with GBW of 60).

    It depends on the rise time or falling time of the 2MHz pulse. The higher the pulse's rise time, the higher the BW of the op amp typically. T_rise*BW = 0.35 is the approx. formula, where 0.35 is derived time constant from 10% to 90%.

    In general case, you would need to 5X to 10X (decade) in design margin to fully reproduce the pulse shape.  For instance, to duplicate a square wave, you would need up to 7X to 13X of a fundamental frequency. >5X of the fundamental frequency signal will produce better edges, small overshoot. Yes, your estimation is correct. 

    With Gain of 3V/V, then you need to multiply the above BW by 3X (GBWP rule). So 30MHz or greater BW in op amp would be recommended, such as OPA328, OPA828. Here are some additional higher BW  op amp selections. 

    https://www.ti.com/amplifier-circuit/op-amps/precision/products.html#23typ=20%3B63&sort=23typ;desc&

    There are some general purpose op amps may work as well (typically lower in cost), but I will check it out and verify its performance.  

    https://www.ti.com/amplifier-circuit/op-amps/general-purpose/products.html#sort=23typ;desc&

    If you have other questions, please let me know. 

    Best,

    Raymond