THS4131: Achievable highest gain

Morning Takashi, 

That should be possible from a Bandwidth standpoint, 

Being an FDA, the concern becomes the loading shown by the required resistors - the input resistor will be the load to the source, and the feedback resistor will be part of the load to to the FDA output, 

So, say the source can drive 200ohm, then for 25dB gain the feedback R needs to be 3.55kohm. If the source cannot drive 200ohm, then scale these up. 

The device has 150MHz GBP, so at that gain should still have over 8Mhz bandwidth

Hello Onawa-san,

  Yes, with the THS4131's gain bandwidth of 170MHz, 25dB or around 18V/V will be achievable for a 10kHz input signal. I have attached a Tina-TI file below of a example MFB Butterworth configuration for 10kHz at 25dB.

  As Michael mentioned, it is important: 

1. Keep feedback/input/outputs between the two sides symmetrical (Video FDA series)
2. Balance inputs including source impedance
3. Balance outputs including loading impedance.

  Each suggestion is linked with an app note that covers these concepts in detail. I can also send you a new excel calculator via email that covers the calculation of these components.

THS4131_10kHz_25dB.TSC

Thank you,

Sima