Difficulty: Easy
Correct Answer: input impedance, common-mode rejection, gain
Explanation:
Introduction / Context:
Instrumentation amplifiers are precision differential amplifiers used for sensor interfacing, biomedical measurements, and industrial data acquisition. They excel at amplifying tiny differential signals in the presence of large common-mode voltages and noise. This question checks whether you know the core performance trio that defines an instrumentation amplifier.
Given Data / Assumptions:
Concept / Approach:
Three hallmarks define instrumentation amplifiers: very high input impedance to prevent sensor loading, very high common-mode rejection ratio (CMRR) to suppress unwanted voltages common to both inputs, and high, accurate gain that is usually set by a single resistor. These traits enable low-level signal extraction with minimal distortion.
Step-by-Step Solution:
Verification / Alternative check:
Datasheets for classic instrumentation amplifiers (e.g., 3-op-amp INA topology) emphasize Zin in megaohms to gigaohms, CMRR often > 100 dB, and gains from 1 to thousands via one resistor, confirming this trio.
Why Other Options Are Wrong:
Noise factor, grounding, power: important system issues, but not the defining trio.
Working voltages, current capacity, output impedance: not the figure-of-merit set for instrumentation amplifiers.
Output gain, output loading, power: vague and incomplete for precision instrumentation needs.
Common Pitfalls:
Confusing general op-amp specs with instrumentation-grade metrics. Overlooking that CMRR is the key measure for common-mode suppression, not just “noise.”
Final Answer:
input impedance, common-mode rejection, gain
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