Introduction:
In a power transistor, the relationship between the base current (IB) and the base-emitter voltage (VBE) is represented by a curve known as the IB vs VBE curve. This curve provides important information about the transistor's operating characteristics and is crucial for understanding its behavior in various circuit configurations.

Explanation:
The correct answer is option 'C' - the IB vs VBE curve of a power transistor resembles the diode curve. This means that the relationship between IB and VBE in a power transistor can be described using the same mathematical equation that represents the current-voltage characteristics of a diode.

The diode curve is characterized by an exponential relationship between the current flowing through the diode and the voltage across it. This exponential relationship is governed by the Shockley diode equation, which is given by:

I = Is * (e^(Vd/Vt) - 1)

Where:
I is the diode current,
Is is the reverse saturation current,
Vd is the voltage across the diode, and
Vt is the thermal voltage (k * T / q, where k is Boltzmann's constant, T is the temperature in Kelvin, and q is the electronic charge).

Similarities between the diode curve and the IB vs VBE curve:
The IB vs VBE curve of a power transistor resembles the diode curve due to the following reasons:

1. Forward bias region: In the forward bias region of the diode, where the voltage across the diode is positive, the diode current increases exponentially with increasing voltage. Similarly, in the forward active region of a power transistor, where VBE is positive, the base current increases exponentially with increasing VBE.

2. Exponential nature: Both the diode curve and the IB vs VBE curve exhibit an exponential relationship between current and voltage. This is because the behavior of the base-emitter junction in a power transistor is similar to that of a forward-biased diode.

3. Saturation region: In the saturation region of the diode, where the voltage across the diode is very high, the diode current reaches a maximum value and becomes almost constant. Similarly, in the saturation region of a power transistor, the base current reaches a maximum value and remains relatively constant.

Conclusion:
The IB vs VBE curve of a power transistor resembles the diode curve due to the similar behavior of the base-emitter junction in a power transistor and a forward-biased diode. Understanding this curve is essential for analyzing the operating characteristics of power transistors and designing circuits using them.