This is the best Instrumentation OpAmp, Great CMRR, ensure supply has no ripple and keep analog and digital grounds separate. Ri can be replaced with a trimpot and resistor to alter gain. Connect a preset ends to pins 1 and 8 and preset wiper to VCC for Offset Null when high gains are configured.
3 Op-Amp Differential Instrumentation Amp
The Input zeners and diodes form a protective clamp for all voltages above VCC-VDD. If supply is changed to +12 -12 change zeners to 12V zeners. Use similar Zeners at output to protect Output from being zapped by overvoltages or high energy - voltage*frequency transients. Add plastic capacitors across Rf for damping AC operation or ripple. Also avoid floating inputs by providing a bias.
This has Virtual Meters and Pots, shows how a Operational Amplifier works. Slide the Potentiometers and vary the mV Source, See Output DVM. Slide the Potentiometers just like you would operate a Sliding Control. Drag the Knob on Pot to increase or decrease the resistance. The Resistance is shown is blue letters and dynamically alters value as you slide the pot. The mV Source is varied by just moving or hovering mouse pointer over the two buttons, no clicking. The mV buttons are special, the variation picks up speed if you let the mouse pointer remain on the button. This is Ramp-up and Ramp-down. This enables you to set it faster with just two buttons.
Instrumentation Differential Amplifier using Three Op-Amps, Slide the Potentiometers and vary the mV Source, See Output DVM. This is close to the Ideal Instrumentation Amp, High Z and Excellent CMRR.
Vout = (Vp - Vn) * (2Rf+Ri)/Ri
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