Scribd
Upload
230 views6 pages

Ece 346 Lab 4

This experiment studied the charge storage transients in a PN-junction diode by measuring the junction capacitance as a function of applied bias. The circuit was constructed from Figure 3 and measurements were taken using an oscilloscope while adjusting the applied voltage. Data was collected on the time constants of current decay and plotted versus the logarithm of the ratio of forward and reverse currents. From the log-log plot of capacitance versus applied bias, values were determined for K, x, and φ0 and compared to ideal models. The computed value of x was found to be close to an ideal linearly graded junction diode.

Uploaded by

LordLawnmower
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOC, PDF, TXT or read online on Scribd
230 views6 pages

Ece 346 Lab 4

This experiment studied the charge storage transients in a PN-junction diode by measuring the junction capacitance as a function of applied bias. The circuit was constructed from Figure 3 and measurements were taken using an oscilloscope while adjusting the applied voltage. Data was collected on the time constants of current decay and plotted versus the logarithm of the ratio of forward and reverse currents. From the log-log plot of capacitance versus applied bias, values were determined for K, x, and φ0 and compared to ideal models. The computed value of x was found to be close to an ideal linearly graded junction diode.

Uploaded by

LordLawnmower
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOC, PDF, TXT or read online on Scribd
You are on page 1/ 6

Ryan Hauser

ECE 346 Experiment #4


11/3/20163
Purpose:
The purpose of this experiment is to study the Charge Storage Transients in a PN-junction Diode. To study the
Junction Capacitance as a function of the applied bias.
Theory:
When the AC voltage switches from a positive to a negative bias, the diode current cannot immediately achieve
steady state values of zero. The diode will continue to conduct until the excess minority carriers are eliminated
from the space charge region and regain their original reverse bias distribution.
Procedure:
We started this experiment by constructing the circuit from Figure 3. Having attached the circuit to the
oscilloscope we measure and observe the signal over the diode. Adjusting the VPP we are able to determine
better results from the circuit.
Data:
Part 1:
ratio of Offset V(V) t=ts Vf=V-Vr (V) Rs Ir=Vr/Rs If=Vf/Rs
(s) Vr=V/( ) () (A) (A)

(V)

1 0 4.68 4.12 2.34 2.34 100 0.0234 0.0234


1.22 0.25 1.25 5.12 0.5631 0.6869 100 0.005631 0.006869
1.5 0.5 4.062 6.16 1.6248 2.4372 100 0.016248 0.024372
1.86 0.75 9.551 7.320 3.33951 6.21149 100 0.033395 0.062115
2.33 1 9.063 8.64 2.72162 6.34138 100 0.027216 0.06341
Part 2:
Junction Capacitance (nF) Applied Bias (-v)
.0047 40
.0049 35
.0051 30
.0055 25
.006 20
.0069 15
.0085 10
.0124 5

Questions:
1. Charge Storage Transients:
1a. Compute the time constants of the current decay from the graphs
drawn. Compute the average .

ts =>

If/Ir t=ts

1 4.12E-6 0.6931472 5.9439E-6


1.22 5.12E-6 0.7975072 6.42E-6
1.5 6.16E-6 0.9162907 7.21387E-6
1.86 7.320E-6 1.0508216 6.96598E-6
2.33 8.64E-6 1.2029723 7.18221E-6
average = 6.71805E-6

1b. Plot t_s versus ln[1+I_f/I_r]

average is the slope of the trend line = 0.088 sec.


j a
2a) Plot C versus V on a log-log graph paper. Determine the values of K, x, and _0.
from equation 4: K = 5.135e^-13, = 400V, x = 0.45b)Compare the computed values of x with an ideal abrupt

junction diode (x=0.5), and an ideal linearly graded junction diode (x=0.5) by using statistical analysis

techniques.
From question 1, we know that our experimental value for x = 0.45. The value is close compared to an ideal
linearly graded junction diode and an abrupt junction diode since there is an average percent error of 18%.
Additionally, our computed value f x is actually closer to the abrupt junction diode which makes more sense
because the IN4004 is an non-linear device and not linearly graded except when it is in reverse bias mode
under a certain condition.
Conclusion:

This lab was helpful to understand theoretical versus practical behavior of diodes.

You might also like