Simulation Lab (EC-406) - Important Questions

Using a SPICE-based simulator (e.g., LTspice or Multisim), simulate the forward and reverse I–V characteristics of a silicon PN diode. From the simulated forward semi-log I–V plot, determine the diode saturation current $I_S$ and the ideality factor $n$. Explain the procedure used to extract $I_S$ and $n$, show the schematic, simulation settings, and include the plots used for extraction.

Simulate a PN diode under a specified DC bias of $V_{D}$ and determine the small-signal (dynamic) resistance $r_d$ and junction capacitance $C_j$ at that bias. Describe how $r_d$ is obtained from the DC I–V curve and how $C_j$ is measured in the simulator. Provide schematic, parameter settings, and plots.

Perform a transient simulation of a PN diode subjected to a step from forward bias to reverse bias. Plot the reverse recovery current and determine the reverse recovery time $t_{rr}$. Explain the significance of $t_{rr}$ for high-frequency rectifier applications and include the simulation waveform and settings.

Simulate the common-emitter output characteristics of an NPN BJT by plotting $I_{C}$ versus $V_{CE}$ for at least four different base currents $I_B$. From the plots, determine the BJT's output resistance $r_o$ at a chosen operating point and estimate the Early voltage $V_A$. Explain the method used for extraction and include the schematic, biasing arrangement, and output plots.

Using a MOSFET model in a SPICE simulator, obtain the transfer characteristic $I_D$ versus $V_{GS}$ at a fixed $V_{DS}$. From the transfer curve, determine the threshold voltage $V_{TH}$ and the small-signal transconductance $g_m$ at a specified bias point. Describe the extraction procedure and provide plots and simulator settings.

Design and simulate a fixed-bias common-emitter BJT amplifier. Determine the DC operating point (collector current and collector-emitter voltage) and perform an AC analysis to obtain the voltage gain $A_v$. Show the schematic, component values, bias calculations, operating point report, and the AC gain plot.

Simulate a full-wave bridge rectifier with a capacitor filter supplying a resistive load $R_L$. Plot the rectified output waveform and measure the ripple voltage. Compare the measured ripple with the theoretical approximation $$\Delta V \approx \frac{I_{load}}{2 f C}$$ where $I_{load}=\left\dfrac{V_{DC}}{R_L}\right$ and $f$ is the mains frequency. Provide the schematic, component values, simulation plots, and calculation steps.

Simulate both half-wave and full-wave rectifier circuits (without and with smoothing capacitor). For a given load and capacitor, obtain the DC output mean and peak-to-peak ripple for each case. Explain why the ripple for the full-wave rectifier is lower and include schematic, settings, and waveform plots.

Design and simulate a positive clamper circuit that shifts a given sinusoidal input so that its waveform is clamped to a specified DC level. Also simulate a series diode clipper that clips the positive peaks above a specified voltage. Provide the circuit diagrams, component values, simulation waveforms, and explain how the clamping and clipping actions are achieved.