Question

In the circuit shown here, the transistor used has a current gain $\beta = 100$. What should be the base resistor $R_B$ so that $V_{CE} = 5 \,V$ (neglect $V_{BE}$)?

• A. $200 \times 10^{3}\,\Omega$
• B. $1 \times 10^{6}\,\Omega$
• C. $500\,\Omega$
• D. $2 \times 10^{3}\,\Omega$

Answer 1

Answer: (A)

Applying Kirchhoff's law to mesh ADCEFA $V_{CC} =10 = I_C \times 10^3 +V_{CE}$
$10 = I_C \times 10^3 + 5$
$I_C = 5 \times 10^{-3}\,A\,\, ...(i)$
Applying Kirchhoff's law to mesh $AGBEFA$
$I_B \times R_B + V_{BE} = V_{CC} = 10\, V$
$I_B \times R_B + 0 = 10 \,\,... (ii)$
$5 \times 10^{-5} \times R_B = 10$
$R_B = 2 \times 10^5 \,\Omega$
$= 200 \times 10^3 \,\Omega$