Topic: Analog Circuits
Determine the change in collector current, $\Delta I_c$ due to change in base emitter voltage VBE from $25^{\circ}C$ to $100^{\circ}C$ for a Silicon Transistor in Fixed Bias Configuration having $\beta=100$. (Consider following variation in Silicon transistor parameters with temperature- At $T=25^{\circ}C$ $V_{BE}=0.65$ V and At $T=100^{\circ}C$ $V_{BE}=0.5~V)$ $R_B=250k\Omega$ $V_{cc}=10V$ $R_c=1 k\Omega$
- A. $60~\mu A$
- B. $30~\mu A$
- C. $15~\mu A$
- D. $120~\mu A$
Answer: A. $60~\mu A$
Explanation: For a fixed bias configuration, the base current is $I_B = \frac{V_{cc} - V_{BE}}{R_B}$. The collector current is $I_c = \beta I_B$. The change in collector current is $\Delta I_c = \frac{\beta (-\Delta V_{BE})}{R_B}$. Given $\Delta V_{BE} = 0.5 - 0.65 = -0.15$ V, $\Delta I_c = \frac{100 \times 0.15}{250 \times 10^3} = 60~\mu A$.