What are open-loop and closed-loop gains of an op-amp?

Op amps are very high gain devices. To achieve stable operation, op-amps are used with negative feedback. The gain of the device alone is called open loop gain, and the gain when configuring a negative feedback circuit is called closed loop gain. Closed-loop gain is not device-specific and is usually determined by the feedback network.

Fig. 1 Bode plot of an op-amp
Fig. 1 Bode plot of an op-amp

Above the cutoff frequency where the gain drops -3dB below the passband, the open-loop gain halves when frequency doubles. (On a logarithmic scale, it has a slope of -6 dB/oct or -20 dB/dec.) .
The closed-loop gain (Gv) of the negative feedback circuit shown in Fig. 2 is calculated as -R2/R1.

Fig. 2 Example of a negative feedback circuit (inverting amplifier)
Fig. 2 Example of a negative feedback circuit (inverting amplifier)

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