Op-Amp

See how a large open-loop gain drives the output toward its limits when the two inputs differ.

V1 applies a ±0.5 V, 100 Hz sine wave to the noninverting input. The inverting input is grounded. With no feedback path, the model’s large differential gain drives the output toward its ±12 V limits. RL = 10 kΩ provides a measurable load.

$$V_{\mathrm{out}}=A_{\mathrm{OL}}(V_+-V_-)$$ $$V_{\mathrm{out}}\approx\operatorname{clip}(A_{\mathrm{OL}}V_{\mathrm{in}},-12\,\mathrm{V},12\,\mathrm{V})$$

The output changes sign near each input zero crossing. Bandwidth gives a finite delay and transition time, so this is not an ideal instantaneous comparator. This example shows why linear amplification normally needs feedback.

Read the results. The saved transient chart uses separate voltage and current panels; the table provides numerical samples. The first voltage probe is green and the second red. The first current probe is blue; a second current probe is purple.

Model limits. The three-terminal op-amp model has implicit ±12 V output limits, 200,000 low-frequency gain and 10 MHz gain-bandwidth product. Supply pins are intentionally absent in this functional model. In Schmitt-trigger and relaxation/integrator oscillator examples, the switching amplifier uses a 100 kHz gain-bandwidth setting to resolve transitions cleanly at the saved time step. It omits detailed slew-rate, input common-mode, output-current and thermal limits.

Try it. Set V1 peak voltage to 0.1 V; even this smaller differential input drives the output near its limits. Restore the original values after comparing the results.