on ujt oscillator

[xljin2006]

hi,friends, the pics are: 1,ujt oscillator circuit. 2, ujt construction etc. 3, ujt Ie--ue relation.

let's begin with oscillator circuit. at first current from vcc through r1 engcharge c1, and emitter voltage of ujt go up, until reach vp, then the pn junction open, for ie-be relation，it is negative resistance region. the question comes next:when be reach uv(valley voltage), why it go back to cut off region, and not continue to saturation region?

thx.

 

[schmitt trigger]

Because C1 becomes discharged and MOST IMPORTANTLY, the R1 value should be high enough such that at the supply voltage of your choosing, the available current is lower than the Valley current.
In equation form:

Vs/R1 < Iv

 

[xljin2006]

in.saturation region, the capacitor is encharging and the current form is:
Ir1=Ic+Ie.can this happen?

 

[danadak]

Explanation ....

UJT Relaxation Oscillator - Working Principle and Circuit Diagram

The Article Gives a Brief Description of UJT Relaxation Oscillator. Its Circuit Diagram. Working Principle, Applications are Given

www.elprocus.com

Regards, Dana.