Lab 8 TF EIM

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 [math] R_{scope}= 1M\Omega[/math]. 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 reverse current [math]I_r \lt 1 \mu A[/math] as a function of the DC supply voltage. (30 pnts)

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.

Bias Volts	V_{scope} (1 M\Omega)(mV)	Current (V/R)	Power

Graph

1. make the same measurements in parts 1 and 2 above for a germanium diode.
2. Plot the diode current (on the ordinate) versus the diode voltage (on the abscissa)for both diodes on the same graph. (50 pnts)

Questions

1. The reverse biased diode acts like a constant ____________. (10 pnts)
2. The forward biased diode has a very __________ resistance. A reverse biased diode has a very ____________ resistance.(10 pnts)
3. The approximate DC forward resistance for diode #___________ is _________ when the forward current is _______________.(10 pnts)
4. The approximate DC reverse resistance for diode #___________ is _________ when the forward current is _______________.(10 pnts)
5. The silicon diode #___________ has an approximate turn on voltage of ___________.(10 pnts)

Forest_Electronic_Instrumentation_and_Measurement