An operational amplifier (op-amp) is an electronic processing component that detects the difference between two input voltages and produces an amplified output. Depending on the circuit, it can act as a comparator, amplifier, or voltage follower.
An op-amp has a non-inverting input , an inverting input , and an output voltage . Its basic open-loop relationship is:
Here, is the very large open-loop gain. Because this gain is extremely high, even a small difference between the inputs can drive the output close to a supply voltage. This is called saturation: the output cannot exceed the limits set by the power supply rails.
| Op-amp configuration | What it does | Output behaviour |
|---|---|---|
| Comparator | Compares two input voltages | Output switches high when and low when |
In amplifier circuits, negative feedback returns part of the output to the inverting input. This stabilizes the circuit and allows external resistors to determine a predictable gain. Op-amps also have high input impedance, so they draw very little current from sensors, and low output impedance, allowing them to drive the next system stage effectively.
A common misconception is that an op-amp always amplifies voltage by its maximum gain. In practice, feedback components control the gain, while an open-loop op-amp commonly functions as a comparator.
For an IB Design Technology A3.4 response, identify the two inputs, explain comparison or feedback, and state how the output responds. When given resistor values, show the correct gain equation and include the negative sign for an inverting amplifier.