Operational amplifier configurations key terms

Inverting amplifier

An op‑amp circuit where the input signal is applied to the inverting (-) input through a resistor, and the output is fed back to the same input via another resistor, producing a voltage gain of –R_f/R_in and a 180° phase shift.

Inverting configuration

The arrangement of an op‑amp where the input is connected to the inverting terminal and the non‑inverting terminal is grounded, resulting in a negative voltage gain and phase inversion.

Phase inversion

A 180° change in the phase of the output signal relative to the input, so the output voltage is opposite in polarity to the input.

Inverting amplifier

An op‑amp circuit that produces an output voltage that is a negative multiple of the input voltage, achieved by feeding the input through a resistor to the inverting (-) input and providing feedback from output to the same node.

non-inverting amplifier

An op‑amp circuit that applies the input signal to the non‑inverting (+) terminal, producing an output that is in phase with the input and has a voltage gain of 1 + Rf/Rin.

voltage gain of a non‑inverting amplifier

The ratio Vout/Vin in a non‑inverting amplifier, calculated as 1 + Rf/Rin.

Voltage gain

Voltage gain is a precise Non-inverting amplifier configuration term in AQA A-Level Physics electronics. Ratio of output voltage to input voltage in an amplifier, expressed as V_out/V_in. When using this term, connect it to the input condition, the relevant component or circuit response, and the output signal, measurement, graph feature, or control effect. This makes the definition curriculum-specific and prevents it becoming a generic electronics phrase.

Non‑inverting amplifier

An op‑amp configuration where the input signal is applied to the non‑inverting (+) terminal, producing an output that is in phase with the input.

Inverting amplifier

An op‑amp circuit where the input signal is applied to the inverting (-) terminal and the output is 180° out of phase with the input.

Non‑inverting amplifier

An op‑amp circuit where the input signal is applied to the non‑inverting (+) terminal and the output is in phase with the input.

Summing amplifier

An op‑amp circuit that combines several input voltages, each through a resistor, to produce an output voltage equal to the weighted sum of the inputs.

Weighted sum of inputs

The output voltage of a summing amplifier is the algebraic sum of each input voltage multiplied by the ratio of the feedback resistor to its input resistor.

Output voltage of a summing amplifier

The voltage produced at the output node of a summing amplifier, obtained by summing the contributions of each input voltage weighted by the ratio of the feedback resistor to its corresponding input resistor.

Voltage gain of a summing amplifier

The ratio of the output voltage to the algebraic sum of the input voltages, determined by the resistor values in the feedback and input paths.

Summing amplifier

An op-amp circuit that combines multiple input voltages into a single output voltage, with each input weighted by its corresponding resistor.

Signal processing

The analysis, modification, and synthesis of signals to extract information or produce desired outputs.

Bandwidth

The range of frequencies over which an op‑amp can amplify a signal with a specified minimum gain, limited by internal capacitances and transistor speed.

Slew rate

The maximum rate of change of the op‑amp output voltage, expressed in V/µs, determined by the internal current source and output stage.

bandwidth

The range of frequencies over which an op‑amp can amplify signals with acceptable accuracy, usually defined by the frequency at which the gain falls to 70.7 % (−3 dB) of its low‑frequency value.

slew rate

The maximum rate of change of an op‑amp’s output voltage, expressed in volts per microsecond, which limits how quickly the output can follow a rapidly changing input.

output saturation

The condition in a real operational amplifier where the output voltage reaches the maximum or minimum supply voltage, beyond which the amplifier can no longer increase or decrease its output linearly.

saturation voltage

The specific output voltage level at which a real op‑amp enters saturation, typically close to the positive or negative supply rails.

Ideal operational amplifier

A theoretical op‑amp with infinite open‑loop gain, infinite input impedance, zero output impedance, and unlimited bandwidth, so that the output voltage is a perfect, linear amplification of the input difference.

Real operational amplifier

A practical op‑amp that has finite open‑loop gain, non‑zero output impedance, limited bandwidth and slew rate, and non‑zero input bias currents, causing deviations such as gain error, phase shift, and output saturation.

Supply voltage

The maximum positive and negative voltages available to the op‑amp, determining the theoretical limits of its output.

Output voltage swing

The range of output voltages the op‑amp can produce, typically slightly less than the supply voltage due to internal voltage drops.

Clipping

The distortion that occurs when the op‑amp output reaches its supply limits and cannot follow the input signal, producing a flattened waveform.

Non‑inverting amplifier

An op‑amp configuration that applies the input signal to the non‑inverting (+) terminal, producing an output that is in phase with the input.

Phase relationship

The relative timing of two signals; in a non‑inverting amplifier the output phase matches the input phase.

Voltage gain

The ratio of output voltage to input voltage, given by 1 + Rf/Rin for a non‑inverting op‑amp.