Chapter 15: The Operational Amplifier Abstraction vocab

Operational Amplifier

A high-gain differential amplifier used as a basic analog circuit building block

Op Amp

The abbreviation for operational amplifier.

Differential Amplifier

An amplifier that responds to the voltage difference between two inputs.

Non-Inverting Input

The op amp input marked plus; increasing its voltage tends to increase output voltage.

Inverting Input

The op amp input marked minus; increasing its voltage tends to decrease output voltage.

Open-Loop Gain

The very large gain of an op amp without feedback

Voltage-Controlled Voltage Source

A source whose output voltage depends on a controlling voltage.

Negative Feedback

Feeding part of an output back to the inverting input to improve controlled linear behavior.

Positive Feedback

Feeding part of an output back to the non-inverting input to reinforce changes and create switching or oscillation.

Closed-Loop Gain

The controlled gain of an amplifier with feedback applied.

Virtual Short

The approximate equality of op amp input voltages under negative feedback and non-saturated operation.

Virtual Ground

A node held near ground voltage by negative feedback without being directly connected to ground.

Non-Inverting Amplifier

An op amp circuit that produces an output with the same polarity as its input.

Inverting Amplifier

An op amp circuit that produces an output with opposite polarity from its input.

Voltage Follower

A unity-gain non-inverting amplifier used for buffering.

Buffering

Isolating a signal source from a load while preserving the signal voltage.

Loop Gain

The gain around an entire feedback loop.

Thevenin Resistance

The equivalent resistance seen at a circuit’s input or output terminals.

Test Source

A known voltage or current applied to find an equivalent circuit resistance.

Adder

An op amp circuit that produces an output related to the sum of input signals.

Subtracter

An op amp circuit that produces an output related to the difference between two inputs.

Integrator

An op amp circuit that produces an output proportional to the negative integral of its input.

Differentiator

An op amp circuit that produces an output proportional to the negative derivative of its input.

Active Filter

A filter made with active devices such as op amps, plus resistors and capacitors.

Miller Effect

The increase in effective capacitance or time constant caused by feedback.

Saturation

The state where an op amp output reaches a limit near a power supply voltage.

Positive Saturation

The state where an op amp output is near the positive supply voltage.

Negative Saturation

The state where an op amp output is near the negative supply voltage.

Comparator

A circuit that compares input voltages and drives its output to one of two saturation states.

RC Oscillator

A circuit using resistors, capacitors, and positive feedback to create a repeating waveform.