The emitter resistance stabilizes the Q-point as it : 

Concept:

In a BJT amplifier circuit, the emitter resistance \( R_E \) is used to stabilize the operating point (Q-point) against variations in temperature or transistor parameters.

This stabilization is achieved through negative feedback: when the collector current \( I_C \) increases due to temperature rise, the emitter current \( I_E \) also increases, causing a larger voltage drop across \( R_E \).

This increased voltage drop reduces the base-emitter voltage \( V_{BE} \), which in turn reduces \( I_C \), thereby counteracting the original increase and stabilizing the Q-point.

Calculation:

Let \( V_{BE} = V_B - V_E \). If \( I_E \) increases, \( V_E = I_E \cdot R_E \) increases, and hence \( V_{BE} \) decreases.

As \( V_{BE} \) decreases, base current and hence collector current decrease, stabilizing the Q-point.