UJT as a relaxation oscillator
The UJT is a highly efficient switch it is used as trigger a device for SCR. No sinusoidal oscillators saw tooth generators phase control and timing circuits. Since UJT shows negative resistance characteristics it is mostly used as a relaxation oscillator. Relaxation oscillator. Initially the voltage across capacitor is zero hence UJT is off in this condition a small reverse leakage current as a emitter current will be flowing. As shown in capacitor C will begin to charge by VBB through resistor R.