List of Op Amp Symbols, Definitions, and Equations

V0 - The Output Voltage

The output voltage for an op-amp circuit is the voltage at the output node, which is determined by the input voltages and the gain of the op amp.

Vs - The Source/Input Voltage

External source of voltage that is fed into the op amp. Defined in the problem, minimal level of mathematics involved.

V+ - The Non-Inverting Input Voltage

The voltage at the positive terminal of the op amp.

V- The Inverting Input Voltage

The voltage at the negative terminal of the op amp circuit.

Vd - The Differential Input Voltage

The differential input voltage is defined as the difference between the non-inverting input voltage and the inverting input voltage; in particular, Vd = v+ - v-

Vf - Feedback Voltage

The feedback voltage is defined as the portion of the output voltage fed back into the circuit.

A - Open-Loop Gain

The internal gain of the op-amp circuit, typically the value is extremely large.

For ideal op-amp circuits, the amp is infinite.

Closed-Loop Gain

The closed-loop gain is defined as the output voltage divided by the source voltage.

Feedback Factor

Loop Gain

Input Currents

i+

i-

Defined as the currents entering into the op-amp terminals

Rin - Input Resistance

The input resistance is defined between V+ and V-; for an ideal op-amp circuit, the input resistance is defined as infinite.

Output Resistance - R0

The output resistance is defined as the internal resistance of the output stage; for an ideal op amp, the output resistance is 0.