The correct answer is:
(a) fo=Unity Gain BandwidthClosed Loop Voltage Gainf_o = \frac{\text{Unity Gain Bandwidth}}{\text{Closed Loop Voltage Gain}}fo=Closed Loop Voltage GainUnity Gain Bandwidth
Explanation:
The break frequency (also known as the corner frequency or -3dB frequency) of an operational amplifier refers to the frequency at which the gain of the op-amp starts to decrease due to the frequency response limitations of the amplifier.
In the context of an op-amp with feedback:
- Unity Gain Bandwidth (UGB): This is a key parameter of an op-amp, which is the product of the bandwidth and the closed-loop gain at which the op-amp can operate. The UGB is a constant value for a given op-amp, and as the gain increases, the bandwidth decreases.
The closed-loop voltage gain refers to the gain of the op-amp when feedback is applied, which reduces the open-loop gain. The break frequency fof_ofo is determined by dividing the Unity Gain Bandwidth by the closed-loop gain.
Thus, the break frequency fof_ofo is given by:
fo=Unity Gain BandwidthClosed Loop Voltage Gainf_o = \frac{\text{Unity Gain Bandwidth}}{\text{Closed Loop Voltage Gain}}fo=Closed Loop Voltage GainUnity Gain Bandwidth
Why the Other Options Are Incorrect:
- (b) fo=Unity Gain BandwidthOpen Loop Voltage Gainf_o = \frac{\text{Unity Gain Bandwidth}}{\text{Open Loop Voltage Gain}}fo=Open Loop Voltage GainUnity Gain Bandwidth: This is not correct because the open-loop gain does not directly define the break frequency for circuits with feedback.
- (c) fo=Unity Gain BandwidthGain of Feedback Circuitf_o = \frac{\text{Unity Gain Bandwidth}}{\text{Gain of Feedback Circuit}}fo=Gain of Feedback CircuitUnity Gain Bandwidth: The gain of the feedback circuit typically refers to the closed-loop gain, not the open-loop gain.
- (d) All of the mentioned: Since (b) and (c) are incorrect, this option is also incorrect.
Therefore, the correct formula for the break frequency is (a), where the Unity Gain Bandwidth is divided by the closed-loop voltage gain.