DIAC

Semiconductor Devices

AIM

To study the VI characteristics of DIAC with positive biasing and plot the curve between V and I.

APPARATUS

  • NV6531 Diac Characteristic Trainer
  • 2mm Patch Cord

THEORY

The diac is a two-terminal device that has three semiconductor layers. It is a bidirectional diode, i.e., it can be made to conduct in either direction. This is just like a TRIAC without a gate terminal. The switching from OFF to ON state can be achieved by simply exceeding the avalanche breakdown in either direction.

CIRCUIT DIAGRAM

PROCEDURE

POSITIVE BIASING

  1. Make the connections as same as the circuit diagram.
  2. Connect the +35V DC supply to the circuit by connecting point 1 with point 4 with the help of a patch cord.
  3. Rotate the potentiometer P1 in the fully anti-clockwise direction.
  4. Now connect point 2 with point 8 to make grounds common.
  5. Connect the voltmeters across the DIAC. For that connect the positive terminal of voltmeter with the point 7 and connect the negative terminal with point 8.
  6. Now connect the Ammeter to the point 5 and negative terminal to the point 6.
  7. Connect the mains cord to the trainer and switch on the supply.

NEGATIVE BIASING

  1. Connect -35V DC Supply to the circuit by connecting the point 3 and point 4.
  2. Repeat the process from steps 3-7.
  3. Now plot the VI curve for taken readings.

OBSERVATION TABLE

POSITIVE BIASING NEGATIVE BIASING
DIAC Voltage (in V) DIAC Current (in mA) DIAC Voltage (in V) DIAC Current (in mA)

RESULT

VI characteristics of DIAC in both positive and negative bias are obtained.

In forward bias, the current increases after V, and in the reverse bias, the current increases after –V.

PRECAUTIONS

  • Connections should be tight.
  • Avoid double connection.