UNIVERSITI PENDIDIKAN SULTAN IDRIS

SFE 3013

BASIC ELECTRONICS

LABORATORY REPORT 3

EXPERIMENTS FOR DIODE CHARACTERISTICS

SITI NOR AMIRA BINTI MOHMAD NOOR

D20091035073

NUR HAFIZAH BINTI ABDU HADI

D20091035072

PENDIDIKAN SAINS

SEMESTER 1 (2011/2012)

LECTURER:

DR SYED ABDUL MALIK SYED MOHAMAD

Experiment 3: Experiments for Diode Characteristics.

Objective:-

1) To understanding the characteristics of each type of diode.

2) To recognize the specification of each type of diode.

3) To learn how to test the characteristics of each type of diode by using various instruments

4) How to Judge the accepted and defective diode.

Apparatus:-

1) KL 21001 linear circuit

2) Experiment module KL 23001

3) Experiment instrument: oscilloscope and digital multimeter

4) Tool: Basic hand tools

5) Materials: as indicated in the KL 23001

Procedure:-

Part A- Experiment for silicon diode

Plotting the V-I characteristics curve of silicon diode (1) using oscilloscope.

1) Fix the module KL 23001 linear circuit lab then located the block marked 23001-

block a.

2) Insert the short circuit jumper clip referring figure 3.1 b

3) The 2.0Vpp, 1Khz sine wave to IN terminal

4) Using channel 2 for Y component to test point TP1 and TP2 then used channel 2 for

X component of oscilloscope to test points TP3 and TP2. TP1 used for vertical input

and TP3 used for horizontal input.

5) Change the display method ad oscilloscope to display the wave at screen.

6) Record the graph at oscilloscope.

Plotting the V-I characteristics curve of silicon diode (2) using digital multimeter.

1) Fix the module KL 23001 linear circuit lab then located the block marked 23001- block a.

2) Insert the short circuit jumper clip referring figure 3.2. the voltmeter and ammeter was

connected.

3) Connect the 12VDC to the .IN. terminal, then adjust VR2 (10 kΩ) to apply

4) voltage to 2 terminals of the diode as shown in Table (1) from 0.1V to 0.7V and

5) view the corresponding I f (forward current). Use VR2 to continuously adjust V f

6) to view how I f will change then record in Table (1).

7) 4 Insert the short-circuit jumper clip by referring to Figure 3.2 and short-circuit clip

8) arrangement diagram in Figure 3.3 (b) (reverse connection). Connect the

9) Voltmeter and Ammeter.

10) 5 Connect 12VDC to the .IN. terminals then adjust VR2 (10 kΩ) to apply reverse

11) voltage to 2 terminals of the diode as shown in Table (2) from 0V to 5V, and view

12) the corresponding I R. Then record in Table (2)

13) 6 Plot the values of Table (1) (2) on the coordinate paper (Fig 2)

Plotting the V-I characteristics curve of germanium diode (3) using digital multimeter.

1. First, fix the module KL-23001 in the KL-21001 Linear Circuit Lab, then locate

the block marked 23001- block a.

2. Insert the short-circuit clip jumper by referring to Figure 3.4 and the short-circuit

clip jumper arrangement diagram in Figure 3.5 (a) (forward connection). Connect

the Voltmeter and Ammeter.

3. Connect the 12VDC to the .IN. terminal, then adjust VR2 (10 kΩ) to applyvoltage to 2

terminals of the diode as shown in Table (3) from 0.1V to 0.7V and view the

corresponding I f (forward current). Then record in Table (3).

4. Insert the short-circuit jumper clip by referring to Figure 3.4 and short-circuit clip

jumper arrangement diagram in Figure 3.5 (b) (reverse connection). Connect

theVoltmeter and Ammeter.

5. Connect 12VDC to the .IN. terminals then adjust VR2 (10 kΩ) to apply reverse

voltage to 2 terminals of the diode as shown in Table (4) from 0V to 5V, and view the

corresponding I R (without breakdown). Then record in Table (4)

6. Plot the values of Table (3) (4) on the coordinate paper (Fig 3).

Plotting the V-I characteristics curve of germanium diode (4) using oscilloscope

1. First, fix the module KL-23001 in the KL-21001 Linear Circuit Lab, then locate the

block marked 23001- block a.

2. Insert the short-circuit jumper clip by referring to Figure 3.6 and the short-circuit

jumper clip arrangement diagram in Figure 3.7.

3. Connect the 2.0 Vp-p, 1 kHz sine wave to the .IN. terminal. Use Channel 2, CH2(Y)

of the Oscilloscope to test points TP1 and TP2. Used Channel 1, CH1(X) of

Oscilloscope to test points TP3 and TP2. TP1 will be used as the vertical input and

TP3 will be used as the horizontal input while TP2 is the common ground point.

4. Change the display method of the Oscilloscope by adjusting .TIME/DIV. knob to, X-

Y. at the .Horizontal. menu (rotate anti-clockwise). View and record the curve on the

Oscilloscope in Fig (4).

5. Adjust VR2 (10 kΩ), then view the change of the curve.

Result and analysis:-

Graph V-I for silicone diode.

This graph show that the voltage is increase when the current is apply. It doesn’t current

leaked. Form theory it has current leaked but we cannot measured it, the value is very small

and our instrument cannot read it. This graph show the voltage vs current is forward biase. If

the diode is reverse biase the current not flow.

Graph V-I for germanium diode.

From this graph, the voltage increase when the current is increase. Then, this graph showed it

has leaked current. From theory, the value of leaked current for germanium is higher than

silicon that why, we can measure the value of leaked current by using digital multimeter. This

forward biase graph. The theorically if diode reverse biase the current not flow. But this graph

show that it has current. This current called saturated current or leaked current.

Data for Silicone diode by using digital multimeter

TABLE 1

Forward (V) 0.1 0.2 0.3 0.4 0.5 0.6

Forward (mA)

0.1 X 10-3 0.3 X 10-3 0.002 0.02 0.17 1.08

Reverse (V) 1.0 2.0 3.0 4.0 5.0 6.0

Reverse (µA) 0 0 0 0 0 0

Data for Germanium diode by using digital multimeter.

TABLE 2

Forward (V) 0.1 0.2 0.3 0.4 0.5

Forward (mA)

0.2 0.3 0.8 1.6 2.6

Reverse (V) -1.0 -2.0 -3.0 -4.0 -5.0

Reverse (µA) -2.3 -3.3 -4.4 -5.5 -7.0

Discussion:-

Rectifier diodes are electronic devices that are used to control the current flow direction in an

electrical circuit. Two commonly used materials for diodes are germanium and silicon. While

both germanium diodes and silicon diodes perform similar functions, there are certain

differences between the two that must be taken into consideration before installing one or the

other into an electronic circuit. In our experiment we used these types of diodes.

Characteristics of silicon diode

The construction of a silicon diode starts with purified silicon. Each side of the diode

is implanted with impurities (boron on the anode side, arsenic or phosphorus on the

cathode side), and the joint where the impurities meet is called the "p-n junction".

Silicon diodes have a forward-bias voltage of 0.7 Volts. Once the voltage differential

between the anode and the cathode reaches 0.7 Volts, the diode will begin to conduct

electrical current across its p-n junction. When the voltage differential drops to less

than 0.7 Volts, the p-n junction will stop conducting electrical current, and the diode

will cease to function as an electrical pathway. Because silicon is relatively easy and

inexpensive to obtain and process, silicon diodes are more prevalent than germanium

diodes.

a. Silicon diodes are excellent general-purpose diodes and can be used in nearly all

electrical circuits where a diode is required.

b. Silicon diodes are more durable than germanium diodes and are much easier to

obtain. While germanium diodes are appropriate for precision circuits, unless there

is a specific requirement for a germanium diode, it is typically preferable to use

silicon diodes when fabricating a circuit.

c. Silicon diodes have a greater ease of processing, lower cost, greater power

handling, less leakage and more stable temperature characteristics than germanium

diodes.

d. Silicon diode is suitable for all high voltage application.

e. It has much smaller leakaged current, only a few nano-Amperes compared to

germanium diode that have 1000 times more leaky than silicon diode.

Characteristics of germanium diode.

Germanium diodes are manufactured in a manner similar to silicon diodes.

Germanium diodes also utilize a p-n junction and are implanted with the same

impurities that silicon diodes are implanted with. Germanium diodes, however, have a

forward-bias voltage of 0.3 Volts. Germanium is a rare material that is typically found

with copper, lead or silver deposits. Because of its rarity, germanium is more

expensive to work with, thus making germanium diodes more difficult to find (and

sometimes more expensive) than silicon diodes.

a. Germanium diodes are best used in low-power electrical circuits (low voltage

application). The lower forward-bias voltage results in smaller power losses and

allows the circuit to be more efficient electrically.

b. Germanium diodes are also appropriate for precision circuits, where voltage

fluctuations must be kept to a minimum.

c. However, germanium diodes are damaged more easily than silicon diodes.

d. Germanium diode’s lower forward drop (0.2V to 0.3V versus 0 .7V to 1.0V) make

them better at small signal detection and rectification.

e. Temperature stability of germanium diode is poor because Germanium is more

sensitive to temperature and sometimes it can be a problem or can be useful.

Specification of silicon and germanium diode

Parameter Germanium SiliconDepletion layer 0.15V 0.6VForward current A few milli-amperes Tens of amperes

Reverse leakage current A few micro-amperes A few nano-amperes

Max. reverse voltage volts Hundreds of volts

Temperature stability poor Good

Junction capacitance Very low (point contact) Comparatively high

From table above it show that the silicon is good stability that why the value that we

get in table 1 the reverse biase has 0 V. That means silicon is good diode. While

germanium has value for reverse biase so it has leaked current. Silicon diode is most

suitable for electronics .

Conclusion:-

From this experiment we can conclude that, we understand about the characteristics of

silicone and germanium diode. They have specification, then from it we also can recognize

which one is silicone or germanium. Besides that, we learn how to test the characteristics of

diodes by using various instrument then we know the germanium has leaked current. And

silicone doesn’t leaked current. So we can judge here, the silicone is more accepted diode

while the germanium is defective diode. Our experiment is verify.

References:-

1) Laboratory manual2) http://www.learnabout-electronics.org/diodes_03.php3) http://www.ehow.com/list_6823105_characteristics-silicon-germanium-diodes.html4) http://wiki.answers.com/Q/

Why_would_you_use_silicon_diodes_instead_of_germanium_diodes