Calculate and record the current values in Table 1. Using these results, plot the forward-biased portion of the I-V characteristic of the diode. Also calculate and record the ac resistance values r D of the diode in Table 1. 2. Determine the equation for the dc load line of the circuit in Figure 3 and plot it on the I−V characteristic obtained in question 1. Note the quiescent point Q where the load line intersects the characteristic curve. Compare this graphically-obtained Q point with the measured Q point from procedure step 4. 3. Using the measurements of procedure steps 4 and 7 , write an expression for the total diode current i o (t). 4. Using Figure 1 as a guideline, draw the peak (maximum and minimum) ac load lines on the diodecharacteristic. Now draw the ac component of the diode voltage V D (t) as shown in Figure 1 and determine the resulting current i 0 (t). Compare the graphically-obtained i 0
(t) with the results obtained analytically in question 3 . Figure 1 1. Connect the following circuit for determining the diode characteristic in the forward-biased region: Figure 2 2. Adjust the supply voltage E to obtain each value of V D in Table 1 and measure the voltage V R across the resistor. Comnlete Table 1 below. 3. To measure the quiescent values, or dc components, of the diode current and voltage, the supply oltage E=3V. Measure and record the dc diode voltage V D and the dc resistor voltage V R . The quiescent liode current can then be calculated using the relationship I Q =V R/R. 4. Connect the following small-signal diode circuit: 5. Set e(t) to 500mVp−p at 1kHz. Using an oscilloscope set for ac input coupling, observe and accurately sketch the ac component of the voltage V D (t) across the diode. 6. To measure the ac voltage V R (t) across the resistor, it is necessary to interchange the diode and the resistor as shown in the following circuit : Figure 4 7. Using an oscilloscope set for ac input coupling, observe and accurately sketch the ac component of the voltage v R (t) across the resistor. Having measured v R (t), the ac component i(t) of the total diode current io i D (t) can be calculated using the relationship V R (t)i(t)= R i(t)= 270Ω2.3173v =8.58 A
