Amplify a small sensor signal

Use a non-inverting amplifier to scale a 50 mV sensor signal.

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Predict the reading, then compare it with the measurement.

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Use a non-inverting amplifier to scale a 50 mV sensor signal.

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Version tested: Prepared circuit opened in the browser on 2026-09-06; no tool version number exposed. Date: 2026-09-06.

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Steps

Screens captured against Falstad CircuitJS Prepared circuit opened in the browser on 2026-09-06; no tool version number exposed on 2026-09-06; the tool may have moved on — the text steps are the contract.

  1. Step 1

    Do
    In the circuit canvas, inspect the 50 mV source, op-amp, and feedback resistor labels.
    You will see
    The feedback resistors show 90 kΩ and 10 kΩ, and the source measurement panel shows 50 mV.
    Why it matters
    Signal conditioning scales weak sensor outputs for an ADC. Identifying the input and feedback path shows which stage supplies that amplification.

  2. Step 2

    Do
    In the circuit canvas, use the feedback resistor labels to calculate the gain 1 + 90000 / 10000.
    You will see
    The 90 kΩ and 10 kΩ labels give a calculated gain of 10.
    Why it matters
    Gain links the smallest useful sensor change to the converter range. The chapter chooses it from measurement limits rather than the largest available setting.

  3. Step 3

    Do
    In the circuit canvas, point at the output wire and read its measurement panel.
    You will see
    The output measures about 499.95 mV, close to the ideal calculation of 500 mV.
    Why it matters
    Comparing raw and conditioned voltage checks the amplification stage. The chapter asks for both values so a later digital number cannot hide a circuit fault.

  4. Step 4

    Do
    In the source’s right-click menu, choose Edit and set Voltage to 0.1 V.
    You will see
    The output wire’s measurement panel rises to about 1 V.
    Why it matters
    A second input checks whether the gain still describes the output. Testing across the useful range provides more evidence than one successful point.

  5. Step 5

    Do
    In the source’s right-click menu, choose Edit and set Voltage to 0.6 V.
    You will see
    The output clips at 5 V instead of reaching the ideal calculation of 6 V.
    Why it matters
    Clipping prevents the output from representing the full input change. The chapter therefore chooses gain that fits the safe voltage range.

  6. Step 6

    Do
    In the source’s right-click menu, choose Edit and restore Voltage to 0.05 V.
    You will see
    The output measurement returns to about 500 mV.
    Why it matters
    Restoring the input checks recovery after the limit test. A clean output alone cannot reveal the information lost while the amplifier was clipped.

Chapter checks

These questions refer to the chapter’s examples. Use the return links to review their answers.

  1. A strain gauge Wheatstone bridge is balanced at zero load with all four 350ohm resistors. Under maximum load, one gauge changes by 0.1% (to 350.35ohm). With 5V excitation, what differential output voltage do you expect?

    Return to the chapter’s knowledge check

  2. A pressure sensor outputs 0-50mV for 0-100 PSI range. You want to interface it with a 3.3V, 12-bit ADC. What amplifier gain provides the best resolution while staying within the ADC input range?

    Return to the chapter’s knowledge check

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