Transconductance in CE amplifier circuit is defined as

Options

A. Ratio of change in collector current to the change in emitter current
B. Ratio of change in input base-emitter voltage to the change in emitter current
C. Ratio of change in collector current to the change in input base-emitter voltage
D. Ratio of change in emitter current to the change in input base-emitter voltage

Answer

To solve the question regarding the definition of transconductance in a common emitter (CE) amplifier circuit, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Transconductance**:
Transconductance, denoted as \( g_m \), is a parameter that measures the efficiency of a transistor in converting input voltage changes into output current changes.

2. **Identifying the Parameters**:
In a common emitter amplifier, we are interested in the relationship between the input voltage and the output current. The relevant parameters are:
- \( \Delta I_C \): Change in collector current
- \( \Delta V_{BE} \): Change in base-emitter voltage

3. **Defining Transconductance**:
The transconductance \( g_m \) is defined mathematically as:
\[ g_m = \frac{\Delta I_C}{\Delta V_{BE}} \]
This means that transconductance is the ratio of the change in collector current to the change in input base-emitter voltage.

4. **Evaluating the Options**:
Now, we need to evaluate the provided options to find which one matches our definition:
- **Option A**: Ratio of change in collector current to the change in emitter current - Incorrect.
- **Option B**: Ratio of change in input base-emitter voltage to the change in emitter current - Incorrect.
- **Option C**: Ratio of change in collector current to the change in input base-emitter voltage - Correct.
- **Option D**: Ratio of change in emitter current to the change in input base-emitter voltage - Incorrect.

5. **Conclusion**:
Based on our analysis, the correct definition of transconductance in a common emitter amplifier circuit is given by **Option C**.