What is Ideal operational amplifier? — Physics

Definition 10.2 University Physics — Year 1 · Chapter 10 — The Operational Amplifier

The ideal model assumes: (i) no current enters either input, $i_+ = i_- = 0$ (infinite input impedance); (ii) the output imposes its voltage whatever the current drawn (zero output impedance); (iii) infinite gain, $\mu \to \infty$ . In the linear regime ( $\abs{V_s} < V_{\mathrm{sat}}$ ) the third assumption forces

\epsilon = V_+ - V_- = 0 :

the two inputs sit at the same potential (a “virtual short circuit”) although no current flows between them.

The operational amplifier: symbol with its two inputs, and its transfer characteristic V_s( ) — a steep linear segment of slope 105 (drawn far too shallow), then saturation at ± V_ sat. In the ideal model the linear segment is vertical: = 0. — The operational amplifier: symbol with its two inputs, and its transfer characteristic $V_s(\epsilon)$ — a steep linear segment of slope $\mu \sim 10^5$ (drawn far too shallow), then saturation at $\pm V_{\mathrm{sat}}$ . In the ideal model the linear segment is vertical: $\epsilon = 0$ .

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