Adder/Subtractor

Adder/Subtractor:

Similarly, it can be shown that the output voltage V₀₄ due to V₄  alone is

V ₀₄= V ₄

Thus, the output voltage Vo due to all four input voltages is given by

V_o= V₀₁+ V₀₂+ V₀₃+ V₀₄

V o=@V₁@V₂+ V ₃+ V ₄

So, the circuit is an adder-subtractor.

Instrumentation Amplifier:

The difference gain of this instrumentation amplifier R, however should never be made zero, as this will make the gain infinity. To avoid such a situation, in a practical circuit, a fixed resistance in series with a potentiometer is used in place of R.

Figure 6(c) shows a differential instrumentation amplifier using Transducer Bridge. The circuit uses a resistive transducer whose resistance changes as a function of the physical quantity to be measured.

The bridge is initially balanced by a dc supply voltage V_dc so that V₁=V₂. As the physical quantity changes, the resistance RT of the transducer also changes, causing an unbalance in the bridge (V₁ ≠V₂). This differential voltage now gets amplified by the three op-amp differential instrumentation amplifier.

There are number differential applications of instrumentation amplifier with the transducer bridge, such as temperature indicator, temperature controller, and light intensity meter to name a few.