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Lesson 6
The ideal op-amp has infinite gain and infinite bandwidth. A real one has a single dominant pole, so every closed loop trades gain for bandwidth, and a limited current behind that pole, so a big signal runs into the slew rate first. Commit to predictions, then fire up the scope and see why.
Predict · 1 of 2 · bandwidth
A non-inverting amplifier, Rf = 9 kΩ, Rg = 1 kΩ, on a general-purpose op-amp: A₀ = 100 dB, GBW = 1 MHz. The ideal model says it is flat for ever. At what frequency is its gain 3 dB down? The Bode shows the op-amp's own open-loop gain; mark your answer on the slider.
Result
Waiting on your call.
Make your mark, then lock it in. The answer, your error and the reason behind it land here, and the scope and every view below fire up.
Engine: small signal from the in-browser MNA solver, with the op-amp as controlled sources (G, E) and its R and C; large signal by RK4 on the same op-amp's two states with its tanh input stage, 5,000 steps over 2 periods to a periodic steady state. Checked against closed forms and against the MNA in its linear limit by scripts/opamp-check.mjs. SPICE: its numbers show once you're in the lab (they'd give the answers away).