Lab Assignment 1

COL215

July 30, 2015

Objective

Familiarization with Spice, basic RLC circuit simulation, diode I-V characteristics anduse of diode as a voltage regulator.

Part 1

1. Download and install LTSpice. (http://www.linear.com/designtools/software/)

2. Simulate a simple resistive circuit with a voltage source, as shown in Figure 1.Take R1 = R2 = 2.5k. Sweep the voltage source from 1V to 5V in steps of 1V,and plot the values of current with time.

Figure 1: A simple resistive circuit

3. Simulate an RC circuit with zero initial conditions, as shown in Figure 2. Plot thevoltage across the capacitor and current through the resistor with time, as shownin Figure 3.

4. Simulate an RLC circuit with zero initial conditions, as shown in Figure 4. Plotthe voltage across the capacitor and current through the inductor with time.

5. Verify that the voltages and currents obtained using Spice are the same as thatobtained theoritically.

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Figure 2: An RC circuit

Figure 3: Current and voltage with time

Figure 4: An RLC circuit

Part 2

1. Plot the i-V characteristics of:

(a) A forward biased diode

(b) A reverse biased diode

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using the circuit shown in Figure 5. Limit the forward current to 100 mA.

Figure 5: A forward biased diode

2. Demonstrate reverse breakdown in a Zener diode. Choose a Zener diode with abreakdown voltage of 6.2 V .

3. Simulate a voltage regulator using a reverse biased zener diode, as shown in Fig-ure 6. Plot the I-V characteristics by sweeping the source voltage from −8 V to18 V . Also plot the voltage across the load resistor versus source voltage and thepower dissipated by the Zener diode with source voltage. Find the value of lineregulation between 16 V and 18 V .

Figure 6: A voltage regulator using a diode

Useful commands in LTSpice

1. Add components: F2

2. Rotate components: Ctrl-R

3. Draw wire: F3

4. Label a wire: F4

5. To plot power dissipation: Alt-Click a component

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6. Add annotations to the plot using Plot Settings > Notes and Annotations

7. Use Tools > Write plot to a .wmf file to save the waveforms

8. Use Tools > Color Preferences to edit colors of the waveforms

9. Export waveform data points to a .txt file using File > Export. (First ensure thatthe waveform window is the active window)

10. View the netlist generated by LTSpice using View > SPICE Netlist.

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