HELP aid my understanding of BJT's (take it slow im new to this... )

[mikeOJ]

using the information provided determine:
IC
VE
VB
R1

just take me through it, would be appreciated, im wondering if it would help to redraw the circuit..??

 

[ericgibbs]

using the information provided determine:
IC
VE
VB
R1

just take me through it, would be appreciated, im wondering if it would help to redraw the circuit..??

hi,
They give you Vc = 10V and Vcc =15V and the collector resistor as 4.7K, so you should be able to tell us the Ic thru the 4.7K..???

What do you think it is.?

 

[mikeOJ]

:S bare with me if im wrong but do you take the voltage drop so 10v-15v=5v and multiply that by the resistor value then divide it by 4.7, giving us 5..

 

[ericgibbs]

:S bare with me if im wrong but do you take the voltage drop so 10v-15v=5v and multiply that by the resistor value then divide it by 4.7, giving us 5..

No, use Ohms Law Ic = [ Vcc-Vc ] / Rc

Now what do you make the Ic current value.??

 

[mikeOJ]

Ohms law.. see i know the principle yet didnt apply it.
ok, so then its 15-10/4.7
so that mean for part ii we can find the VE using the Ic and IB

 

[ericgibbs]

Ohms law.. see i know the principle yet didnt apply it.
ok, so then its 15-10/4.7
so that mean for part ii we can find the VE using the Ic and IB

Its important to calculate the Ic current, from that assuming that the current into the base is 'zero', this would mean the same current flowing in the 1.2K resistor is 'virtually' the same as the current thru the 4k7.

However there MUST be a small current Ibase flowing into the base of the transistor other wise no collector current would flow in the 4.7K.
Work out this small Ibase current and add it to the emitter current, let me know what you get

Obviously I am trying to give you clues on how to solve this problem on your own, rather than just giving you the answer.

 

[Grossel]

I got the answer right in my hand. I've assumed HFE=100 and Vbe=0,6V just for easy. I need to refresh my memory too sometimes

See atachment

 

[ericgibbs]

I got the answer right in my hand. I've assumed HFE=100 and Vbe=0,6V just for easy. I need to refresh my memory too sometimes

See atachment

This is a HOMEWORK question, the OP is supposed to work it out himself, not be given the answer.

 

[Grossel]

This is a HOMEWORK question, the OP is supposed to work it out himself, not be given the answer.

I know homework question too. But fortunately he will learn something about this. Either one of:
* "I'm stuck but here's what I have got so far"
* "The answers (numbers as stated above) helped me to solve the issues"

This guy actually have two replies to the given suggestions on this forum (as opposed to most other students just don't throw out a copy of their homework and we never hear from them again). Personally I think he dererve some help. Now, If he responds, we get a clue if he got it right or not.


@mikeOJ - Did you get this right?