Terminator3
Advanced Member level 3
I am learning S53MV oscillator design. It is provided here: http://lea.hamradio.si/~s53mv/spectana/vco.html
I want to understand how biasing was chosen for BFP420 bjt transistor. I cant find any I-V (Ib) curves in BFP420 datasheet. Prevously i biased FET ne3210s01 and it was pretty convient, because there was some I-V curves, where i can draw Q point and load line. Although it was for certain conditions. But here, with BJT i do not know how to do that. So i did some forward and reverse calculations:
As you see i found that
VCE is around 4v and current Ie=15ma. Then Rb and Rc was determined. Sow how, based on bfp420 datasheet i can choose emitter current and Vce? Or how i can know iv characteristics. Did i choose beta(hfe),etc. right?
I want to understand how biasing was chosen for BFP420 bjt transistor. I cant find any I-V (Ib) curves in BFP420 datasheet. Prevously i biased FET ne3210s01 and it was pretty convient, because there was some I-V curves, where i can draw Q point and load line. Although it was for certain conditions. But here, with BJT i do not know how to do that. So i did some forward and reverse calculations:
Code:
Vbe=0.6; ' V
Vcc=8; 'V
hfe=60;
Ic=14.8*10^-3; 'A
Vce=3.9; 'V
Ib=Ic/hfe
Ib = 0.000246667
Rc = (Vcc- Vce)/ Ic
Rc = 277.027027027
'S53MVS Rc= 270 Ohm
Rb = (Vcc - Vbe - Ic*Rc) / Ib
Rb = 13378.378378378
' S53MVs Rb = 6.8+6.8 = 13.6 kOhm
' Reverse calculations to find Q point
Rc=270;
Rb=13600;
Ie=(Vcc-Vbe)/(Rb/hfe+Rc)
Ie = 0.014899329
Ic=Ie;
Vce=-Ic*Rc+Vcc
Vce = 3.977181208VCE is around 4v and current Ie=15ma. Then Rb and Rc was determined. Sow how, based on bfp420 datasheet i can choose emitter current and Vce? Or how i can know iv characteristics. Did i choose beta(hfe),etc. right?
