A realistic graph depiciting the variation of thhe reciprocal of input resistance in an in- put charcteristics measurement in a com- mon emitter transistor configuration is :

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Answer

To solve the question regarding the variation of the reciprocal of input resistance in a common emitter transistor configuration, we will follow these steps:

### Step 1: Understand the Input Characteristics of a Common Emitter Transistor
In a common emitter configuration, the input characteristics are typically represented by a graph of base current (IB) versus base-emitter voltage (VBE). The input resistance (r_in) can be defined as the ratio of the change in base-emitter voltage (ΔVBE) to the change in base current (ΔIB).

### Step 2: Define the Reciprocal of Input Resistance
The reciprocal of input resistance (1/r_in) can be expressed as:
\[ \frac{1}{r_{in}} = \frac{\Delta I_B}{\Delta V_{BE}} \]
This means that as the input resistance increases, the reciprocal decreases, and vice versa.

### Step 3: Sketch the Input Characteristics Graph
1. Plot the base-emitter voltage (VBE) on the x-axis and the base current (IB) on the y-axis.
2. The graph typically starts at the origin (0,0) and shows a nonlinear increase in IB with increasing VBE.
3. The graph will show a threshold voltage (around 0.6V to 0.7V for silicon transistors) where the current starts to increase significantly.

### Step 4: Analyze the Graph for Reciprocal of Input Resistance
1. For low values of VBE (below the threshold), the base current IB is very small, leading to a high input resistance.
2. As VBE increases, IB increases, and thus the reciprocal of input resistance (1/r_in) also increases.
3. After reaching a certain point, the graph will start to level off, indicating that further increases in VBE result in smaller increases in IB, leading to a decrease in the rate of change of IB with respect to VBE.

### Step 5: Draw the Final Graph
1. The final graph should show a curve that starts steep, indicating high resistance, then flattens out as VBE increases, indicating lower resistance.
2. The x-axis (VBE) will be labeled, and the y-axis (1/r_in) will also be labeled.

### Conclusion
The realistic graph depicting the variation of the reciprocal of input resistance in a common emitter transistor configuration will show an initial steep rise followed by a leveling off as VBE increases.

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