Electrical Engineering › Section Q · Thyristors, operational amplifiers, and power conversion › Topic Q.7
Differential and instrumentation amplifiers
Many sensors produce a tiny difference riding on a large shared voltage. A four-resistor difference amplifier extracts that difference with a set gain, and the three-op-amp instrumentation amplifier does it with high input impedance and a gain set by a single resistor.
In this topic
- Measuring a difference, not a voltage
- The four-resistor difference amplifier
- Worked example: a difference amplifier
- Common-mode gain and CMRR
- Worked example: a 1% mismatch
- Two practical weaknesses
- The instrumentation amplifier
- Worked example: a strain-gauge amplifier
- Why the design works so well
- Common mistakes to avoid
- Key takeaways
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