E84 Home Work 10

1. The circuit shown in the figure contains a voltage source $V=10V$, two resistors $R_1=300\Omega$ and $R_2=200\Omega$, and a silicon diode. Find the voltage $V_D$ across and the current $I_D$ through the diode. Solve this problem in two different methods: (a) assume voltage $V_D=0.7$ (as the diode is always forward biased), and (b) use the graphic approach to find the intersection of the load line and the diode equation:
   
   $$I_D=I_0 ( e^{V_D/\eta V_T}-1 )$$
   
   
   Sketch the plot of the two curves and estimate the solution $(I_D,V_D)$ at their intersection. (Note that you can assume $I_0=10^{-10}$ and $V_T=0.026V$ at room temperature 300K.)

   

2. The circuit shown in the figure contains a voltage source $V=10V$, three resistors $R_1=300\Omega$, $R_2=200\Omega$, and $R_3=100\Omega$, and two silicon diode. Find the voltage across the two parallel branches. (Hint: assume $V_D=0.7$ when the diode is forward biased.)

   

3. The circuit shown in the figure is a converter (adaptor) based on a full-wave rectifier, which gets an AC voltage input of 115V 60 Hz, and produces a 12V DC output. The voltage variation or ripple of the output should not exceed 5% when the load current is no more than 2A. Design the converter in terms of the turn ratio of the transformer and the value of the capacitor.

   

4. The input voltage to the circuit in the following figure is $v(t)=10 \sin (\omega t)$. The two DC voltages are both 5V. Sketch the waveform of the output voltage $V_{out}$.

   

5. Assume each of the input voltages $V_1$ and $V_2$ takes one of two values, either 0V or 5V. Find the output voltage $V_{out}$ in the following combinations of three input:

   $V_1$	0V	0V	5V	5V
   $V_1$	0V	5V	0V	5V
   $V_{out}$