UJT Relaxation Oscillator

AIM 

To construct a UJT relaxation oscillator and plot the wave forms at emitter, base 1 and base 2.

COMPONENTS AND EQUIPMENTS REQUIRED

• Resistors                          100 Ω             2 nos.
• Capacitor                          0.1 μF             1 no.
• UJT                                   2N2646          1 no.
• Power supply                   10 V DC         1 no.
• Oscilloscope                    0 to 20 MHz  1 no.
• Multimeter                                                1 no.
• Breadboard                                               1 no.
• Connecting wires

THEORY:

 UJT is a unipolar device. It is constructed using an N type silicon bar on which a P type silicon material is doped. It has three terminals namely base1 (B1), base2 (B2) and emitter (E). The RC circuit associated with UJT will function as a relaxation oscillator. The sharp pulse available from the circuit can be used as trigger pulse for various applications. Once the power supply is switched ON, Capacitor C charges through R towards VBB. Then the voltage across the capacitor reaches Vp (= ηVBB+ Vd), where η = 0.63, Vd = 0.7V, UJT turns ON and it enters a negative resistance region. The capacitor rapidly discharges through UJT, since it then offers very low resistance. This sudden discharge develops a sharp pulse at B1. When the capacitor voltage reaches valley voltage (Vv) of UJT it turns OFF. This enables the capacitor to charge again and repeat the cycle.

PROCEDURE

• Check the given components and assemble in a bread board as per circuit.
• Connect the output of the circuit to an oscilloscope and Switch ON the power supply
• Plot waveforms

CIRCUIT DIAGRAM

OBSERVATIONS

RESULT

Constructed an UJT relaxation oscillator and plot the wave forms at emitter, base1 and base2.