+ -
Experiment 5
EE 312
Basic Electronics Instrumentation Laboratory
Wednesday, September 27, 2000
Objectives:
• Si Rectifier Forward I-V Characteristics
– Forward Conduction
• at Room Temp (T)
• at Elevated Temp (IVT Method)
• Characteristics of Zener Diodes
– Forward Conduction at Room Temp
– Reverse Conduction at Room Temp
Background:
Two Types
Semiconductor Diode Vacuum Tube Diode
Semiconductor Diodes:
Anode
+ Anode
I
- Cathode
One Way
Cathode - Anode
I
+ Cathode
Types of diodes:
670H16 IN4742
Zener, Si Ge
metal case Glass case
Anode
Cathode
ID
ID
VD
VD
R
ID External Limit
VD
1/RD
Diode Piece-wise approximation
VT
Reverse
bias (V)
Reverse current (uA) Forward current (mA)
Ge
Si
Tu
be
bias(V)
Forward
Parameters:
• Maximum average forward current (IF,Max)
– Full-cycle average current IF that the diode can safely
conduct without becoming overheated
• PRV, PIV,or VRM All mean the same
– peak reverse voltage
– peak inverse voltage
– voltage reverse, maximum
(Maximum allowable reverse-bias voltage for the diode)
PRV rating of 200 V means that the diode may breakdown &
conduct & may even be destroyed, if the peak reverse voltage is
greater than 200 V
• Surge or fault current (ISurge)
– The amount of momentary overload current I surge the
diode can withstand without being destroyed
• Temperature Range
• Forward voltage drop (VF)
– VF across the diode when it is conducting, given at the
maximum average forward current
• Maximum reverse current (IR,Max)
– Maximum current IR the diode can handle for sustained
period of time when operated as a Zener Diode
• Other Parameters
– Base diagram, total capacitance, reverse recovery time,
recommended operating ranges
Forward
Characteristics
ID
breakdown
voltage I F,Max
PRV
VF VD
Reverse
Characteristics
IR,Max
~
~ IS
Forward
Characteristics
ID
/dI
Rd y n=dV
IF
Rd=VF/IF
VF VD
Reverse
Characteristics
∆VD
Rzener =
∆ ID
Procedures:
1- Silicon Rectifier (IVT)
Forward I-V at 21 C
Forward I-V at ~45 C & ~70 C
2- Silicon Zener Diode (I-V)
Forward I-V at 21 C
Reverse I-V at 21 C
3- PSPICE Simulation (Bell 242)
Components:
• Silicon Rectifer (VBD < 200 V)
• Si Diode (Zener, VBD ~ 27 V or ~ 12 V)
• 0.1, 1.0, 4.7 kohms 2Watt Resistors
• Heater Block & Tube Insulator
• Temperature Probe
• Variac (Shock Warning: Not Isolated
From Power Line)
1- Forward Characteristics of Diodes
R Ω DMM
I
DMM
+
10._ V V
- ID
Vary R from 100 k to 100
VD
R Ω
I
+
10.__V Vdc V
-
Rectifier & Zener
R Vdc Id Vd
[ohm] [V] [mA] [V]
100k 10.38 0.01 0.380
. . . .
. . . .
. . . .
100 10.822 100 0.822
2-Reverse Characteristics of Zener Diode
(at voltages below breakdown)
4.7 k Ω DMM
I
²1kS DMM
+
0-40V 28V V
- ID
VD
VOLTS DC CONSTANT-VOLTAGE
DUAL TRACKING CURRENT-LIMITED
FLOATING
POWER SUPPLY
+
V 20V
-
+ +
0-20V 1A COMMON 0-20V 1A V 20V
- 40V
+
+5@1A
V 20V
-
-
2-Reverse Characteristics of Zener diode
(at breakdown region)
1kΩ DMM
I
DMM
+
0-40V V
- ID
VD
1kΩ DMM
I
DMM
+
0-40V V
-
Id Vd
[A] [V]
Zener
0.1: 0.001
. .
. .
. .
9.9m 29.0
3- Simulation (PSPICE)
D1 2 0 Diode
.Model Diode D(IS=1E-14 RS=5 N=1 BV=25 IBV=1E-10)
default: Unit:
IS Saturation current 1.0E-14 A
RS Ohmic resistance 0 Ohm
N Emission Coefficient 1 -
BV Reverse breakdown voltage infinite V
IBV Current at breakdown voltage 1.0E-3 A
ISR, NR, IKF, NBV, IBVL, NBVL, TT, CJO, VJ, M
FC, EG, XTI, TIKF, TBV1, TBV2, TRS1, TRS2, KF,
AF
5- Temperature Characteristics of Ge Diode
Thermocouple
Probe “Hot Block”
Ceramic
Tube Heaters
Ge Diode
to Variac
5 cm
Temperature Probe converter Box
switch
Fluke
Multimeter
200 mV range
1 mV/degree Probe
Temperature Dependence of IS
See Sedra/Smith, TABLE 3-1, p. 156
Insert expression for the intrinsic carrier concentration ni2
into the expression for the the saturation current IS
IS = C1 X T3 X exp(-EG/kT) where C1 is a constant
The T3 temperature dependence is weak compared to the
exponential temperature dependence so that
IS = C2 X exp(-EG/kT) where C2 = C1 X 3003
lnIS = ln(C1 X 3003 ) - EG/kT
Temperature Dependence of I S
See Sedra/Smith, TABLE 3-1, p. 156
Insert expression for the intrinsic carrier concentration n i2 into the expression for the the saturation
current IS
IS = C1 X T3 X exp(-EG/kT) where C1 is a constant
The T 3 temperature dependence is weak compared to the exponential temperature dependence so that
IS = C2 X exp(-EG/kT) where C2 = C1 X 300 3
lnIS = ln(C1 X 3003 ) - EG/kT
Precautions:
• Always turn off the Variac and set its dial to zero
when not using it.
• At the start of the lab period, preheat the “hot
block” to 40C. When you get to part 5, insert the
diode into the block and allow a few minutes for
the temperature to stabilize.
• Do not exceed a temperature of 75C in the “hot
block.”
• Do not exceed the current rating for the diode:
– Ge: IF, Max = 100 mA I R,Max = 1.0 mA
– Si: I F,Max = 100 mA I R,Max = 100 mA
Must Submit Electronic
Version Using Command
submit ee312 E5ReportTuAM#
Paper Version Also Required
Team Writing
• Abstract & Report for Zener Diode reverse
IV on the 1999 web
• Introduction to be provided or omitted
• One Partner does silicon rectifier IVT
results & discussion for IS & n
• Must provide results in a computer file to
Partner in less than one week & submit to
EE 312 Staff using submit command.
• Other Partner uses information provided by
partner to determine EG. Also include
discussion and conclusions . Submit report
electronically within one week of receiving
partner’s contribution. Paper version also.
• PSPICE Simulations Not Required.
• Late penalties are -10 points per day and the
day starts at 9:00 AM.
