Question

In the circuit shown here the transistor used has a current gain $\beta =100$. What should be the bias 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

The correct option is A $200\times {10}^3\Omega$

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)
$5\times {10}^{-5}\times R_B=10$
$R_B=2\times {10}^5\Omega =200\times {10}^3\Omega$.