Mayank
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Hello Diapankar, I think you are simulating a Trans-Impedance Amplifier. H(f) is nothing but the Impedance offered by the block & as you correctly put it, it's VoutDIFF / IinDIFF . The reason that it's a Trans-Impedance Block is because you are tapping you output in the form of a Voltage. Loop Dynamics will be decided by the way the Opamp sees it's input. When inside the loop, the opamp's only function is to keep Vin+ & Vin- voltages at it's input terminals very close to each other, so as to provide a finite output Voltage. So, for stability analysis, you better look at the Loop Gain Plot rather than the V/I Plot.
Also, as aaron pointed out, feeding inputs to your ckt is also v imp. I think the best way is to use an ideal balun and give some ac current as well as DC current & generate some DC bias at input nodes through a Resistor to Ground.
thanks, Mayank.
btw, returning to Designer's Guide after a long break. Hi all !!
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