PSF of bipolar transistor

Hy i have a question about an exercise and i try but i don't understand wy give me wronk.
The schematic is below.
I want to find static PSF of transistor,IC,IB and VCE but i don't understand why emiter voltage is not equal with (RE2/RE2+RE1)*VEE.I simulated circuit in Ltspice and voltage is different from my.Can you help me?If someoane have a book or course with random exercices with BJT and MOS,like this with ansure will be great.Pls i wan't to learn!!

(RE2/RE2+RE1)*VEE ignores the transistor completely and just gives you the voltage divided from VEE.

No gain is given for the transistor so it is impossible to tell how much current it passes but assuming this is a small signal transistor (based on the values around it) the gain will be fairly high and the transistor close to saturation so it will behave somewhat like a diode, dropping Vbe across it. If you remove Ra and the transistor and imagine them to be a 0.6V constant voltage drop it will make the calculation easier.

Brian.

For finding the DC currents and voltages you must solve a set of 3 equations involving the voltages VE, VC and IC.
Furthermore, during these calculations you must use some assumptions: VBE=0.7V, IE=IC and B=IC/IB=150 (example).
The result will be between IC=0.5 and IC=1mA (depending on the B value used).

Alberto Dan said:

Hy i have a question about an exercise and i try but i don't understand wy give me wronk.
The schematic is below.
I want to find static PSF of transistor,IC,IB and VCE but i don't understand why emiter voltage is not equal with (RE2/RE2+RE1)*VEE.I simulated circuit in Ltspice and voltage is different from my.Can you help me?If someoane have a book or course with random exercices with BJT and MOS,like this with ansure will be great.Pls i wan't to learn!!
View attachment 133747

Click to expand...

Easy solution with one equation. The Thevenin resistance of the emitter resistor-voltaqe network is rth = 821 ohms, and the Theveniin voltage vth = --3.42 volts.

Do the loop through the emitter and base to collector.

vth+(beta+1) ib rth+0.7+200000 ib+(beta+1) 5000 -5.0 =0

Solving for ib gives ib=7.72/(200000+5821(beta+1))

Select your beta and find your ib. Once you know ib and beta, you can find ic. ic for beta 150 is 1.07 ma.

What is PSF? You should define acronyms before using them unless they are very common.

Ratch

Hey Ratch - good job! Thanks to Thevenin.

Thx all for yours help!!Anybode know some books where i find more like this exercices?

Hy,sory but i don't understand why Vth is -3.42V,how you calsulated?If calculate Thevenin in emiter of transistor not give us -5V?And Rth gives me 1k2.I aplied thevenin on resistor RE2.I want to find voltage across it.I simulated this in Ltspice and resultat is below.I don't understand wy Vemitter is equal to -2.61V.Can you help me again please?

Alberto Dan said:

Hy,sory but i don't understand why Vth is -3.42V,how you calsulated?If calculate Thevenin in emiter of transistor not give us -5V?And Rth gives me 1k2.I aplied thevenin on resistor RE2.I want to find voltage across it.I simulated this in Ltspice and resultat is below.I don't understand wy Vemitter is equal to -2.61V.Can you help me again please?View attachment 133794

Click to expand...

You don't need LTSpice for this simple problem. Perhaps you should study circuit theory more and do some exercises involving Thevenin's theorem. That theorem is widely explained on the web and electrical textbooks.

Ratch