LTC6253 - GBP 720MHz, but gain of 10 = BW of ~35MHz??


I am trying to design a circuit to achieve a gain of 10 for input signals up to 50MHz. I have looked at LTC6253 as a possibility, since it has quite a large GBP of 720MHz. If my understanding is correct, for a gain of 10, it should handle up to 720/10 = 72MHz

I have done a simulation on LTSpice, of non-inverting op-amp with a gain of 10 but it shows that the bandwidth would end up being around 35Mhz.... See screenshot below. 

The datasheet recommends to use a capacitor in the feedback loop to compensate stray capacitances (C1 in my simulation). Through trial and error I have found this to be around 0.5pF.

It seems there are other parameters I need to consider when selecting my op-amp for this application. Does anyone have any suggestions as to what causes a reduction in effective bandwidth vs what I would have expected from the GBP?




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  • Hi Qbort:  The 2GHz spec is the gain-bandwidth-product.  It is the product of gain and frequency at a relatively low frequency.   In this case, the GBW product was specified at 10MHz, and indicates a typical gain of 200 (46dB) there. 

    In a gain of 10, consulting the Gain-Phase curve, you should expect a bandwidth of about 85MHz (on a 5V supply, less on a 3V supply).  I suspect the problem is that your resistor values are too high, so you are up against the feedback pole and necessary compensation.  I suggest you try again with resistor values of 200:450 instead of the 1k:9k, and you should be able to get significantly higher bandwidth.