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Non-Inverting Op-Amp Design Tool

Analyze a known feedback network or select Rf and Rg for a target positive gain. Then check resistor tolerance, input common mode, output swing, bandwidth, slew rate, bias-current error, network current, power, and resistor thermal noise.

Known-network analysisRf / Rg sizingE24 / E96 roundingRange & dynamic checks
01 / Define the stage

Gain network and signal

Defaults are illustrative. Use guaranteed limits for the exact op amp, supply, load, temperature, and frequency.

Rg returns to VREF. Ground-referenced circuits use 0 V.
Required input and output range
Dynamic requirements
Resistor tolerance, bias, offset, and noise inputs

This is a first-order design model. It does not approve stability, capacitive loading, distortion, protection, layout, device noise, overload recovery, or rail behavior.

02 / Review the result

Gain, range, and dynamic checks

Calculated from the current inputs.

Entered requirements have margin
Review the detailed checks before selecting an op amp.
Nominal closed-loop gain—Positive voltage gain
Selected Rf / Rg—Actual preferred-value result
Nominal output at DC point—Before tolerance and op-amp error
Modeled closed-loop bandwidth—Dominant-pole estimate
Non-inverting op-amp feedback networkVin connects to the non-inverting input. Rf connects the output to the inverting input, and Rg connects the inverting input to VREF. +−VINVOUTVREFRfRg
Ideal closed-loop relationship: VOUT = VREF + (1 + Rf/Rg) × (VIN − VREF). Supply, decoupling, load, compensation, and protection connections are omitted.
Theoretical sized resistor
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Actual gain versus target
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Resistance-only gain range
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Required output envelope
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Usable output window
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Input common-mode range used
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Modeled gain loss at signal frequency
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GBW required for allowed loss
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Required slew rate
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Large-signal sine ceiling
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Maximum feedback-network current
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Maximum Rg / Rf power
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First-order op-amp error bound
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Resistor-only output noise density
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Design checks

    Treat the result as a resistor and operating-point plan. Confirm the exact device’s input common-mode range, output swing versus load, gain stability, GBW, slew rate, input/output protection, input bias behavior, noise, distortion, supply current, and layout guidance.

    The download stays on this device and does not submit an RFQ.

    Understand the network

    What the calculator is solving

    The non-inverting input receives the signal directly. Negative feedback holds the inverting input near the same voltage while Rf and Rg set a positive closed-loop gain of at least one.

    Gain and reference

    G = 1 + Rf / Rg
    VOUT = VREF + G(VIN − VREF)
    Rf = (G − 1)Rg
    Rg = Rf / (G − 1)

    VREF shifts the transfer relationship. It does not create supply headroom, and it must remain sufficiently low impedance for the feedback current.

    Tolerance and first-order error

    Gmin = 1 + Rf,min / Rg,max
    Gmax = 1 + Rf,max / Rg,min
    Eop ≈ Gmax|VOS| + Gmax|IB+|RS + |IB−|Rf,max

    The tool adds independent absolute limits conservatively. Temperature drift, correlation, CMRR, PSRR, source error, reference error, and calibration are separate.

    Bandwidth and slew

    fc ≈ GBW / G
    Loss ≈ 10log10[1 + (f/fc)²]
    SRrequired = 2πfVOUT,peak

    The bandwidth estimate assumes a voltage-feedback op amp with a dominant-pole response. Slew rate is a large-signal limit and does not guarantee distortion performance.

    Gain and dominant-pole bandwidth model: Analog Devices MT-033 — Voltage Feedback Op Amp Gain and Bandwidth.

    Before choosing the orderable part

    Translate the circuit into device requirements

    A correct resistor ratio is only the beginning. Use the calculated operating envelope to screen the op amp, passive parts, package, and board conditions.

    Electrical limits to confirm

    • Input common mode: every expected VIN value, including startup and fault behavior.
    • Output swing and current: required load, feedback current, temperature, and supply rails.
    • Dynamics: GBW, slew rate, settling time, distortion, and closed-loop gain stability.
    • Accuracy and noise: VOS, drift, bias current, CMRR, PSRR, voltage/current noise, and resistor tracking.

    Implementation limits to confirm

    • Source and load: impedance, capacitance, ADC kickback, cable effects, and external protection.
    • Reference node: impedance, noise, decoupling, current path, and startup behavior.
    • PCB: feedback-loop area, input guarding, decoupling, grounding, and thermal gradients.
    • Procurement: full suffix, package, grade, qualification, lifecycle, quantity, and evidence requirements.
    Quick answers

    Non-inverting op-amp design questions

    Why can the non-inverting gain not be less than one?

    With the ordinary Rf/Rg feedback network, gain is 1 + Rf/Rg, so positive finite resistances produce a gain greater than one. A voltage follower reaches unity gain. Attenuation needs a separate input divider or another topology, and that divider changes noise, impedance, and error.

    Can Rg connect to a voltage other than ground?

    Yes. If Rg returns to VREF, the ideal transfer is VREF + (1 + Rf/Rg)(VIN − VREF). The reference must support the feedback current and remain low impedance over the required frequency range. Check startup and saturation when VIN or VREF is absent.

    Should I always use large resistor values to reduce current?

    No. Large values reduce feedback current but increase resistor thermal noise and make bias current, leakage, and parasitic capacitance more important. Very small values increase source and output loading. Choose a practical range using the selected op amp’s datasheet and the accuracy, power, bandwidth, and noise goals.

    Does GBW divided by gain guarantee the usable bandwidth?

    No. It is a dominant-pole estimate for suitable voltage-feedback op amps. Closed-loop flatness, phase margin, higher-order poles, capacitive load, source impedance, compensation, and large-signal behavior can reduce usable performance. Confirm the datasheet curves and, where needed, simulation and measurement.

    Why check input common mode when the output is inside range?

    The positive input follows VIN, so VIN itself must remain inside the guaranteed common-mode interval. An output that appears mathematically valid does not make the input stage linear. Some devices also have special behavior near or beyond the rails.

    Does the tool choose an op amp automatically?

    No. It converts the circuit requirement into measurable limits. Device selection still depends on supply, signal range, load, accuracy, noise, stability, package, temperature, qualification, lifecycle, and the latest manufacturer documentation.

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    Technical references

    1. Analog Devices MT-033: voltage-feedback op-amp gain and bandwidth relationships.
    2. Analog Devices MT-038: input bias current and offset-current considerations.
    3. Texas Instruments — Op Amps for Everyone: practical op-amp design, operating range, error, and stability context.
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