Question

Consider the circuit shown below:

$\text{If}{V}_{BE}=0.7V,\text{then the voltage}{v}_0\text{is (Assume}{I}_{\infty }\text{is negligible)}$

• A. 0.5 V
• B. 0.4 V
• C. 0.7 V
• D. 0.6 V

Answer 1

The correct option is B 0.4 V


The Thevenin's equivalent circuit between the terminals A and ground is

$V_{th}=-5V$
$R_{th}=\left(10k\Omega \right)||\left(10k\Omega \right)$
$=5k\Omega$

$I_1=\frac{-5+10-0.7}{4200+\frac{5000}{1+49}}$
$I_1=\frac{4.3}{4300}=1mA$
$I_2=\frac{49}{50}mA$
$I_3=I_2\times \left(\frac{\beta }{1+\beta }\right)$

$I_3={\left(\frac{49}{50}\right)}^{2}mA$
$=0.9604mA$
$V_0=10-(10\times {10}^3\times I_3)$
$V_0=10-9.604=0.396V$