Instrumentation and Summation Configuration-Operational Amplifiers Types Tutorials Series
https://ingenuitydias.blogspot.com/2014/06/instrumentation-and-summation.html
Instrumentation Amplifier Configuration
Some applications, such as an oscilloscope input, require differential amplification with extremely high input resistance(Circuit is shown above)
================================================
Related Tutorials
Operational Amplifiers Tutorials Series
Op-amp Integrator Network
Op-amp with T-bridge Feedback Network
Voltage Follower and Difference Amplifier Configuration
Linear Op-amp Operation-Inverting And Non-Inverting Configuration
A3 is a standard difference op-amp with differential gain R2/R1
A1 and A2 are additional op-amps with extremely high input resistances at v1 and v2 (input currents = 0)*Differential gain of input section:
–Due to the virtual shorts at the input of A1 and A2, we can write iA = (v2 – v1) /RA
–Also, iA flows through the two RB resistors, allowing us to write v02 – v01 = iA(RA + 2 RB)
– Combining these two equations with the gain of the A3 stage, we can obtain
vOUT = (R2/R1)(1 + [2RB/RA])(v1 – v2)
vOUT = (R2/R1)(1 + [2RB/RA])(v1 – v2)
– By adjusting the resistor RA, we can adjust the gain of this instrumentation amplifier
Summation Amplifier Configuration
–The gain for any input k is given by RF/Rk
If any input goes positive, vOUT goes negative just enough to force the input v- to zero, due to the virtual short nature of the op-amp
–Combining all inputs, we have
vOUT = -RF(v1/R1 + v2/R2 + .. + vN/RN)
–The input resistance for any input k is given by Rk due to the virtual short between v- and v+
Posts
.jpg)
.jpg)
