Where is the external feedback network connected in a closed-loop op-amp circuit to control the gain?

In a closed-loop operational amplifier (op-amp) circuit, the external feedback network is connected from the output to the inverting input. This configuration is essential for controlling the gain of the op-amp.

When feedback is provided from the output to the inverting input, it allows for a portion of the output voltage to be fed back into the op-amp, effectively reducing the overall gain of the system. This feedback mechanism ensures that the op-amp operates in a linear region, providing more stability and accuracy in amplification compared to an open-loop configuration, where the gain is typically very high.

In this setup, the inverting input receives the feedback signal, which influences the difference between the voltages at the inverting and non-inverting inputs, allowing for controlled behavior of the amplifier. The gain can be set by the resistor values in the feedback network, adhering to the principle that the output is a function of the difference between the inputs.

This configuration is fundamental in operational amplifier applications like amplifiers, filters, and other analog circuits, where precise control over gain is needed.