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3.4: Procedure

  • Page ID
    26132
  • 3.4.1: Forward Curve

    1. Consider the circuit of Figure 3.3.1 using R = 1 k\(\Omega\). For any positive value of E, the diode should be forward biased. Once E exceeds the knee voltage, all of E (minus approximately 0.7 volts) drops across R. Thus, as E increases, so does the diode current.

    2. Build the circuit of Figure 3.3.1 using R = 1 k\(\Omega\). Set E to 0 volts and measure both the diode's voltage and current and record the results in Table 3.5.1. Remember, voltage is measured across a device (parallel) while current is measured through it (series). Repeat this process for the remaining source voltages listed.

    3. From the data collected in Table 3.5.1, plot the current versus voltage characteristic of the forward biased diode. Make sure \(V_D\) is the horizontal axis with \(I_D\) on the vertical.

    3.4.2: Reverse Curve

    4. Consider the circuit of Figure 3.3.2 using R = 1 k\(\Omega\). For any positive value of E, the diode should be reversed biased. In this case, the diode should always behave like an open switch and thus no current should flow. If no current flows, the voltage across R should be zero, and thus the diode voltage should be equal to the applied source voltage. Note that the diode's voltage polarity is negative with respect to that of Figure 3.3.1.

    5. Build the circuit of Figure 3.3.2 using R = 1 k\(\Omega\). Set E to 0 volts and measure both the diode's voltage and current and record the results in Table 3.5.2. Repeat this process for the remaining source voltages listed.

    6. From the data collected in Table 3.5.2, plot the current versus voltage characteristic of the reverse biased diode. Make sure \(V_D\) is the horizontal axis with \(I_D\) on the vertical.

    3.4.3: Practical Analysis

    7. Consider the circuit of Figure 3.3.3 using E = 12 volts, R1 = 10 k\(\Omega\) and R2 = 4.7 k\(\Omega\). Analyze the circuit using the ideal 0.7 volt forward drop approximation and determine the voltages across the two resistors. Record the results in the first two columns of the first row (Variation 1) of Table 3.5.3.

    8. Build the circuit of Figure 3.3.3 using E = 12 volts, R1 = 10 k\(\Omega\) and R2 = 4.7 k\(\Omega\). Measure the voltages across the two resistors. Record the results in columns three and four of the first row (Variation 1) of Table 3.5.3. Also compute and record the percent deviations in columns four and five.

    9. Reverse the direction of D1 and repeat steps 7 and 8 as Variation 2 in Table 3.5.3.

    10. Return D1 to the original orientation and reverse the direction of D2. Repeat steps 7 and 8 as Variation 3 in Table 3.5.3.

    11. Reverse the direction of both D1 and D2, and repeat steps 7 and 8 as Variation 4 in Table 3.5.3.

    3.4.4: Computer Simulation

    12. Repeat steps 7 through 11 using a simulator, recording the results in Table 3.5.4.

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