The document discusses the electrical characteristics and testing of uni junction transistors. It describes the original uni junction transistor as a bar of N-type semiconductor material with a P-type diffusion. It also describes the programmable uni junction transistor which consists of four P-N layers with an anode, cathode, and gate. Both are used as trigger devices for thyristors and in relaxation oscillators due to their negative resistance characteristic. The document provides instructions to test a programmable uni junction transistor by measuring resistances between the emitter, base 1, and base 2 in different configurations.

1. ELECTRICAL CHARACTERISTICS

2. ELECTRICAL CHARACTERISTICS

3. TEST CIRCUIT

4. TEST CIRCUIT

5. types of Uni Junction Transistors The original Uni Junction Transistor (UJT) a simple device that is essentially a bar of N type semiconductor material into which P type material has been diffused somewhere along its length.

6. types of Uni Junction Transistors 2. The Programmable Uni Junction Transistor (PUT) is a close cousin to the Thyristor consists of four P-N layers has an Anode and a Cathode connected to the first and the last layer, and a Gate connected to one of the inner layers. They are not directly interchangeable with conventional UJTs but perform a similar function.

7. types of Uni Junction Transistors For both types, their main use is as a trigger device for thyristors and as the active device in relaxation oscillators. The graph of emitter voltage against emitter current of a Uni Junction Transistor shows an area of negative resistance; this is what makes it very useful.

8. TEST PUT Test 1 Set a Digital Multimeter in the Ohms position. Read the resistance between Base 1 and Base 2. Read the resistance between Base 2 and Base 1 (reversing the leads). Both of the readings should approximately be equal (high resistance).

9. TEST PUT Test 2 Connect the negative lead to the Emitter. Measure the resistance from Emitter to Base 1 using the positive lead. Measure the resistance from Emitter to Base 2 using the positive lead. Both of the readings should approximately be equal (high resistance).

10. TEST PUT Test 3 Connect the positive lead to the Emitter. Measure the resistance from Emitter to Base 1 using the negative lead. Measure the resistance from Emitter to Base 2 using the negative lead. Both of the readings should approximately be equal (low resistance).