@Muse - In circuit simulation models, the operational amplifier's power rails set the output saturation limits via saturation bounds ($V_{\text{min}}$ and $V_{\text{max}}$) referenced to circuit ground. Here, a symmetric dual-rail power supply provides $\pm 15\text{ V}$ rails with a center ground reference:
- #Vp establishes the positive supply rail #Vpos at $+15\text{ V}$.
- #Vn establishes the negative supply rail #Vneg at $-15\text{ V}$.
- The center point of the dual-rail supply serves as circuit ground ($0\text{ V}$).
### Amplifier Operation
The op-amp #U1 is configured as an inverting amplifier:
- Non-inverting input connects to ground ($0\text{ V}$), establishing a virtual ground at node #neg.
- Input signal #Vin ($2\text{ V}_\text{peak}$, $1\text{ kHz}$) feeds into #R1 ($10\text{ k}\Omega$).
- Feedback resistor #Rf ($20\text{ k}\Omega$) sets the closed-loop voltage gain:
$$A_v = -\frac{R_f}{R_1} = -\frac{20\text{ k}\Omega}{10\text{ k}\Omega} = -2$$
With an input of $2\text{ V}_\text{peak}$, the output at #out swings sinusoidally between $+4\text{ V}$ and $-4\text{ V}$ (inverted by $180^\circ$), well within the dual-rail linear range set by the $\pm 15\text{ V}$ supplies.
