K. J.
Somaiya College of Engineering, Mumbai-77
(Autonomous College Affiliated to University of Mumbai)
Department of Electronics Engineering
Batch: A4 Roll.no: 1622018
Experiment / assignment / tutorial No.1
Grade: AA / AB / BB / BC / CC / CD /DD
Signature of the Staff In-charge with date
Title: DIAC CHARACTERISTICS
Aim: 1) To study V/I characteristics of DIAC DB3 and find its resistance in 3 operating
regions.
2) To identify negative resistance region in the characteristic.
Apparatus:
DIAC DB3, Voltmeter, Ammeter, multimeter, resister, breadboard
COs to be achieved:
CO 1: Understand clearly the various Power Electronics Devices with their strengths
and weaknesses and gain ability to design turn on and turn off circuits with protection
circuits.
Theory:
(Attach theory in a separate sheet). Mention cross-sectional view, operating
principle, circuit symbol. Attach data sheet of DB3 DIAC
Department of Electronics Engineering
PE /Jan -April 18
K. J. Somaiya College of Engineering, Mumbai-77
(Autonomous College Affiliated to University of Mumbai)
Department of Electronics Engineering
Stepwise-Procedure:
1. Connect the circuit as shown in figure.
2. Initially set current measuring multimeter in scale of microampere.
3. Apply variable supply voltage from 0 V to 60 V. in steps of 5V and
measure voltage across DIAC (VDIAC) and current flowing through it
(IDIAC).
4. Once the current increases sufficiently it will be indicated on the ammeter as out
of range, change the scale to milliampere range.
5. Increase supply voltage in small steps near curve to get accurate reading
and continue measuring VDIAC and IDIAC.
6. Now reversing the polarities of the supply, repeat the steps from 2 to 5
7. Plot IDIAC versus VDIAC and note down forward and reverse turn on voltage of
DIAC. Also note the voltage when device comes out from negative
resistance region.
Circuit Diagram:
Resistor Ratings- 2.5 KiloOhm/5 Watts
RANGES:
Input Voltage: 0-60V
Ammeter: 0-20mA
Voltmeter: 0-30V
Department of Electronics EngineeringPE /Jan -April 18
K. J. Somaiya College of Engineering, Mumbai-77
(Autonomous College Affiliated to University of Mumbai)
Department of Electronics Engineering
Observation Table: At least 20 readings
Department of Electronics Engineering
PE /Jan -April 18
K. J. Somaiya College of Engineering, Mumbai-77
(Autonomous College Affiliated to University of Mumbai)
Department of Electronics Engineering
Graphs: (Draw and attach relevant graph)
Department of Electronics Engineering
PE /Jan -April 18
K. J. Somaiya College of Engineering, Mumbai-77
(Autonomous College Affiliated to University of Mumbai)
Department of Electronics Engineering
Calculation: - 1) Resistance in non-conducting region:-
2) Resistance in –ve resistance region:-
3) Resistance in conducting region:
Results:
1. VBOF = 30.2V
2. VBOR = -30.4V
3. IBO = 50uA
4. IF = 0.30A
5. V = 5V
Conclusion:
Thus we studied about DIAC and its characteristics, and also observed the characteristics
by plotting a graph of the readings obtained by performing the experiment.
Department of Electronics Engineering
PE /Jan -April 18
K. J. Somaiya College of Engineering, Mumbai-77
(Autonomous College Affiliated to University of Mumbai)
Department of Electronics Engineering
Post Lab Questions
1. What do you mean by breakover voltage symmetry and dynamic breakover
voltage? Specify its value from experiment and datasheet.
Ans: Breakover voltage symmetry (VBO) is the maximum breakover voltage
range with a specified capacitance when DIACs are connected in parallel.
Dynamic breakover voltage
For a DIAC, this is the dynamic variation of its voltage at triggering. It is the
difference between VBO and the voltage for a 10mA current.
ΔV = VBO - VDIAC(10mA)
2. How the term DIAC is obtained?
Ans: The DIAC is a full-wave or bi-directional semiconductor switch that can be
turned on in both forward and reverse polarities. The DIAC gains its name from the
contraction of the words DIode Alternating Current switch.
3. What is the significance of – ve resistance region?
Ans: Negative resistance is a property exhibited by certain electronic devices, where the
current-voltage relation is inversed, i.e. the current value Increases with a decrease in
voltage and vice versa. Negative resistance is used in fast switching applications.
Date: Signature of faculty in-charge
Department of Electronics Engineering
PE /Jan -April 18
