# Lab 8 TF EIM

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Lab 8 The Diode Objective: Measure the current-voltage curve of a silicon diode.

# Reverse current

1.) Construct the circuit below using a DC power supply, a diode.

2.) Attach an Oscilloscope with internal resistance . The scope will measure the voltage drop across R and thus the current will be given by this voltage difference divided by R.

3.) Determine a value for R which will allow you to measure a current of at least 10 mA (prefeferably 50 mA) at the diodes reverse bias cut off voltage. Show your power calculation. (5 pnts)

4.) Measure the diode reverse current as a function of the DC supply voltage.

 Bias Voltage V_{scope} Current (V/R) Diode power R power

5.) Fill in the blank. The reverse biased diode act as a constant _______________ source. (5 pnts)

# Forward Current

1.) now swap the diode direction and repeat the measurement in the previous section.

2.) Attach an Oscilloscope with internal resistance . The scope will measure the voltage drop across R and thus the current will be given by this voltage difference divided by R.

3.) Determine a value for R which will allow you to measure a current of at least 10 mA (prefeferably 50 mA) at the diodes reverse bias cut off voltage.

4.) Measure the diode forward current as a function of the DC supply voltage.

 Bias Voltage V_{scope} Current (V/R) Diode power R power

5.) Fill in the blank. The forward biased diode act as a constant _______________ source. (5 pnts)

# Graph

1. Plot the diode current (on the ordinate) versus the diode voltage (on the abscissa)for the forward and reverse biased diode on the same graph. (35 pnts)

# Questions

1.) Plot the reverse biased diode for voltages beyond the turn on voltage and measure the effective impedance of the diode using a linear fit. (20 pnts)

2.)The measured reverse biased turn on voltage is _________ Volts for silicon diode type # IN_____________. The % difference between the measured turn on voltage and the one given in the specification is __________%. Circle the correct answer in the parentheses. This % difference (is / is not) within the measurement uncertainty. ( 10 pnts)

3.) Plot the forward biased diode and measure the effective impedance of the diode using a linear fit in the linear region at large bias voltages. ( 20 pnts)

# Show and tell

1.) Use a two channel oscilloscope in "x-y" mode to illustrate the V-vs-I curve to your instructor.

2.) Create a circuit to cause an LED to illuminate.