In an inverting amplifier configuration, what determines the gain of an op-amp?

In an inverting amplifier configuration, the gain is primarily determined by the ratio of the feedback resistor to the input resistor. This relationship is derived from the principle that the operational amplifier (op-amp) will maintain a virtual short between its inverting and non-inverting inputs, effectively allowing us to define the gain mathematically as the negative ratio of these two resistors.

When feedback is applied through a resistor connected from the output to the inverting input, and another resistor connects the inverting input to the input signal, the gain can be expressed with the formula: Gain (A) = -Rf/Rin, where Rf is the feedback resistor and Rin is the input resistor. This shows that adjusting these resistors directly alters the gain of the amplifier, demonstrating that the configuration is critically dependent on these components.

Factors like power source voltage can influence the maximum output swing of the op-amp but do not affect the gain calculation. Similarly, the internal architecture of the op-amp and the load impedance play roles in factors like performance and stability rather than directly determining the gain in this configuration. Thus, the combination of the feedback and input resistors is the key element that defines the gain of an inverting amplifier.