Op-amp with T-bridge Feedback Network-Operational Amplifiers Types Tutorials Series

Op-amp with T-bridge Feedback Network-To build an op-amp with high closed-loop gain may require a high value resistor R2 which may not be easily obtained in integrated circuits due to its large size

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A compromise to eliminate the high value resistor is the op-amp with T-bridge feedback network, shown below :-
–RA and RB comprise a voltage divider generating node voltage vB = vOUT RB/(RA + RB), assuming that R2 >> RA||RB

–Since vB is now fed back to v-, an apparent gain vB/vIN = -(R2/R1) can be written.

Combining these two equations allows us to write vOUT = - (R2/R1)([RA+ RB]/RB)vIN

Fairly large values of closed-loop gain can be realized with this network without using extremely large IC resistors.