Op-amps

An operational amplifier is a kind of difference amplifier.

• Output voltage, $V_{out}$, is the input voltage, $V_{in}$, amplified by a gain, $A_0$, called the open-loop gain.
• Input voltage, $V_{in}$, is the difference between the non-inverting and inverting terminals, $V_{+}$ and $V_{-}$, respectively.

The output voltage is clipped by the supply voltages (also called voltage rails). For example, if $A_0=1[V/\mu V]$ and $V_{in}=1V$, $V_{out}$ would not go all the way to $1,000,000V$, and instead only max out at $V_{DD}$. Typically, $V_{SS}$ is ground but can also be $V_{SS}=-V_{DD}$.