Lesson 1Calculating bandwidth and stability: closed-loop bandwidth from op-amp GBW, phase margin considerations, and compensation techniquesWe work out closed-loop bandwidth from the op-amp's gain-bandwidth product and feedback factor, linking phase margin to stability and response speed. We cover fixes for capacitive loads and high gains with practical design tips.
Relate GBW, feedback factor, and bandwidthInterpret Bode plots and phase margin targetsIdentify signs of marginal or unstable loopsDesign compensation for capacitive loadingCheck stability across process and temperatureLesson 2Practical component selection: finding and interpreting op-amp datasheets (examples of sensor-grade amplifiers)This part shows how to read and pick op-amp datasheets for sensor work. You'll check noise, offset, input range, power options, and packages, learning to quickly match parts to your system's needs.
Identify sensor-grade amplifier familiesInterpret input offset and drift specificationsEvaluate noise, CMRR, and PSRR parametersCheck input and output voltage rangesAssess package, power, and cost constraintsLesson 3SPICE simulation plan for amplifier block: stimulus sources (differential sine, common-mode, noise sources), AC analysis, transient, noise analysis, and offset/error measurementsThis part sets up a clear SPICE plan for the amplifier, with test signals, analyses, and checks. You'll confirm gain, bandwidth, noise, offset, and common-mode performance before PCB layout.
Define simulation objectives and key metricsSet up differential and common-mode sourcesPlan AC, transient, and noise analysesMeasure gain, offset, and linearity in SPICEOrganize testbenches for reuse and reviewLesson 4Designing for input impedance: techniques to achieve high differential and common-mode input impedanceWe look at ways to get high input impedance for differential and common-mode signals using op-amp setups, buffers, and resistors, while managing bias currents, leaks, and bandwidth limits.
Define differential and common-mode impedanceUse buffer stages to isolate sensor loadingControl bias currents and leakage pathsGuarding and PCB techniques for high ZTrade-offs between impedance and bandwidthLesson 5Design documentation checklist: listing calculations, assumptions, part numbers, and margin analysis for PCB handoffThis part outlines a solid docs package for amplifier and sensor designs, noting calculations, assumptions, parts, and safety margins so PCB teams can build and check the circuit with confidence.
List design assumptions and operating conditionsRecord key equations and intermediate calculationsDocument part numbers and critical parametersCapture margin analysis and derating choicesDefine required tests and acceptance criteriaLesson 6Op-amp key parameters and selection process: input noise density, input bias current, input offset, GBW, slew rate, CMRR, PSRR, and supply rangeWe go over key op-amp specs for sensor interfaces and set up a reliable picking process. Focus is on noise density, bias current, GBW, slew rate, CMRR, PSRR, and supply fit for the job.
Relate GBW and slew rate to signal bandwidthUnderstand input noise density and filtersBias current and source impedance interactionCMRR, PSRR, and supply rejection needsStep-by-step op-amp selection checklistLesson 7Resistor networks and gain calculation for differential amplifiers and instrumentation amps: deriving gain equations and loading effectsWe figure out gain formulas for standard differential and instrumentation amps, including resistor rules and loading. Key points are matching, CMRR, and how sensor/ADC loads change actual gain.
Gain equations for basic differential stagesThree-op-amp instrumentation amp gain designImpact of resistor matching on CMRR and gainLoading from sensor and ADC input impedanceSelecting resistor values and power ratingsLesson 8Setting amplifier target specifications: gain, bandwidth, input impedance, offset, drift, and noise budgetThis part shows how to turn sensor needs into amplifier goals for gain, bandwidth, input impedance, offset, drift, and noise. You'll make a short specs table to steer circuit and part choices.
Translate sensor and ADC requirementsDefine gain, bandwidth, and headroom limitsSet input impedance and loading constraintsAllocate offset and drift performance goalsCreate a formal amplifier spec tableLesson 9Understanding differential sensor signals: source impedance, common-mode, and differential-mode conceptsThis part explains how differential sensors work, covering source impedance, common-mode level, and signal range. You'll see how these shape noise, loading, and amp type plus reference choices.
Define differential and common-mode componentsCharacterize sensor source impedance vs frequencyDetermine allowable common-mode voltage rangeRelate sensor specs to amplifier input limitsPlan cabling, shielding, and reference routingLesson 10Topology selection for small differential signals: instrumentation amplifier, differential amplifier, and difference-stage with front-end buffer — trade-offs and use casesThis part compares instrumentation amps, basic differential amps, and buffered difference setups for tiny signals. You'll weigh CMRR, noise, input range, cost, and layout ease for each.
Review classic differential amplifier stageThree-op-amp instrumentation amplifier useBuffered difference stage with front-end gainCompare CMRR, noise, and input rangeGuidelines for topology selection by sensorLesson 11Offset and drift budgeting: calculating expected DC error from input offset, bias currents, resistor tolerances, and thermal effectsWe build a DC error budget mixing op-amp offset, bias currents, resistor mismatches, and temp drift. You'll set error limits, tally worst-case and statistical totals, and link to sensor precision.
Define DC accuracy and allowable error budgetModel input offset and bias current effectsInclude resistor tolerance and mismatch termsAccount for temperature coefficients and driftCompare worst-case versus RSS error methodsLesson 12Noise sources in low-level signals: Johnson noise, amplifier input-referred noise, and environmental interferenceWe spot and measure noise in faint sensor signals from resistors, amp inputs, and surroundings. We cover ways to model, budget, and cut total noise.
Johnson noise of resistors and sensorsOp-amp voltage and current noise modelsInput-referred versus output noise conceptsEnvironmental and interference coupling pathsNoise budgeting and reduction strategiesLesson 13Expected simulation plots and measurements: gain vs frequency, phase, input-referred noise, output noise spectrum, transient response to 1 kHz sine, and worst-case offset scenariosThis part lists key sim plots and checks. You'll tie Bode plots, noise spectra, transients, and offset tests back to specs and error budgets.
Gain and phase versus frequency Bode plotsInput-referred and output noise spectraTransient response to sine and step inputsOffset versus common-mode and temperatureCompare simulated and measured performance
