HdrChopper
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Hi
You can easily derive it by finding using thevenin equivalent circuits. You can use the concept of hemi-circuit, based on the fact you are analyzing a fully diff (purely symmetrical circuit). If you split the input circuit (Z1/Z3/Z1), you'll get a simple resistor divider equal to Z3/2÷(Z3/2+Z1). That is the input impedance of your input voltage source. Z2 does not play a role in the transfer function assuming the op amp's input impedance is >> Z2.
From this you get H=-(Z4*(Z3/2 + Z1)) / (Z3/2)
Hope this helps Tosei
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