SaM - Instrumentational Amplifier

Memory Card

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• Online Resource: Wikipedia
  
• Formula:$V_{out}=(V_2-V_1)\cdot \left(1+\frac{2R_1}{R_{\text{gain}}}\right)\frac{R_3}{R_2}$
• Circuit (with numerical values):
  
• Why should I use an Instrumentational Amplifier instead of a Simpler Differential Amplifier?
  • The IA typically has a higher input impedance compared to a simple Differential Amplifier, since the inputs are feed directly to other operational amplifier.
  • It has a Better Common-Mode Rejection Ratio (CMRR)
  • Also the Instrumentation Amplifiers often offer the flexibility to adjust the gain to suit specific application requirements.

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• Online Resource: Wikipedia
  
• Formula:$V_{out}=(V_2-V_1)\cdot \left(1+\frac{2R_1}{R_{\text{gain}}}\right)\frac{R_3}{R_2}$
• Following my own calculations:${\frac{V_{out}}{V_1}|}_{V_2=0}=-\frac{R_1}{R_{\text{gain}}}\cdot \left(\frac{R_3}{R_2+R_3}\frac{R_2+R_3}{R_2}\right)-\left(\frac{R_1}{R_{\text{gain}}}+1\right)\cdot \frac{R_3}{R_2}$And:${\frac{V_{out}}{V_2}|}_{V_2=0}=\left(\frac{R_1}{R_{\text{gain}}}+1\right)\cdot \left(\frac{R_3}{R_2+R_3}\frac{R_2+R_3}{R_2}\right)+\frac{R_1}{R_{\text{gain}}}\cdot \frac{R_3}{R_2}$So we can say:$V_{out}=\left[\frac{2R_1}{R_{\text{gain}}+1}\frac{R_3}{R_2}\right]V_2-\left[\frac{2R_1}{R_{\text{gain}}+1}\frac{R_3}{R_2}\right]V_1$So:$V_{out}=\frac{2R_1}{R_{\text{gain}}+1}\frac{R_3}{R_2}(V_2-V_1)$

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