For a negative feedback amplifier as shown in the figure, the type of feedback present in the circuit is
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To identify feedback quickly:
If feedback connects to the same node as the output load $\rightarrow$ Shunt sampling.
If feedback connects to a different terminal than the input signal (e.g., input to base, feedback to emitter) $\rightarrow$ Series mixing.
Step 1: Understanding the Question:
The task is to identify the feedback topology of the given negative feedback amplifier.
Feedback topologies are defined by how the feedback network samples the output (either voltage/shunt or current/series) and how it mixes the feedback signal at the input (either voltage/series or current/shunt). Step 2: Key Formula or Approach:
- Output connection: If the feedback network is connected directly in parallel with the output node (sampling the output voltage), it is Shunt sampling.
- Input connection: If the feedback signal is mixed in series with the input voltage source (typically at the emitter or source terminal of the input transistor), it is Series mixing. Step 3: Detailed Explanation:
• Output Sampling: The output voltage $V_{out}$ is taken from the emitter of the second stage transistor $Q_2$. The feedback network consisting of $R_2$ and $C_2$ connects directly to this output node. This parallel connection across the output voltage represents Shunt sampling (voltage sampling).
• Input Mixing: The input signal $V_{in}$ is applied to the base of the first transistor $Q_1$. The feedback signal is fed back to the emitter of $Q_1$ across $R_{E1}$. This means the feedback signal is added in series with the input loop ($V_{be} = V_{in} - V_f$). This arrangement represents Series mixing.
• Therefore, the overall feedback configuration is Series-Shunt (also called voltage-series feedback). Step 4: Final Answer:
The feedback present in the circuit is Series-Shunt feedback, which matches Option (A).
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