Simple Transistor: Basics, Types & Uses

[Duave]

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[Jony130]

Your answer is not correct. You forget about 150K resistor.

Maybe this circuit will be easy for you to solve, you can even use nodal analysis.

Also notice that I1 = (Ib + I2)

Or you can replace voltage divider with his thevenin equivalent circuit.

 

[Duave]

Your answer is not correct. You forget about 150K resistor.

Maybe this circuit will be easy for you to solve, you can even use nodal analysis.

Also notice that I1 = (Ib + I2)

Or you can replace voltage divider with his thevenin equivalent circuit.

Here is a revised version of the solving for VB using KVL
This is question 2(a).

Thank you for any help that you can offer.

Did I answer the question correctly and thoroughly? Can you please find any errors, and point them out to me so that I can fix them?

Homework Statement

2(a): Calculate VB including loading of the bias network by the BJT

Homework Equations

I_E = I_C + I_B
............
V_CC-(I_B)(R_B) -(I_E)(R_E)-(V_BE) = 0
...................

The Attempt at a Solution

https://scontent-b.xx.fbcdn.net/hphotos-frc1/t1.0-9/1964876_10151943479145919_1107480603_n.jpg


Is the answer correct for V(B)? If not, where are the errors located?

Thanks again for your help.

 

[Jony130]

I_E = I_C + I_B
............
V_CC-(I_B)(R_B) -(I_E)(R_E)-(V_BE) = 0
...................

.

You have error already in the the second expression. Are you sure that this is correct KVL/KCL for this circuit? Can you tell me where do you see RB resistor in this circuit ?
The KCL for VB node is I1 = I2 + Ib

Or why you don't try to use thevenin's theorem and replace R1 and R2 and Vcc with his equivalent circuit (Rth and Eth)?

 

[Duave]

You have error already in the the second expression. Are you sure that this is correct KVL/KCL for this circuit? Can you tell me where do you see RB resistor in this circuit ?
The KCL for VB node is I1 = I2 + Ib

Or why you don't try to use thevenin's theorem and replace R1 and R2 and Vcc with his equivalent circuit (Rth and Eth)?

Could Rb= Rb1||Rb2?

 

[Duave]

You have error already in the the second expression. Are you sure that this is correct KVL/KCL for this circuit? Can you tell me where do you see RB resistor in this circuit ?
The KCL for VB node is I1 = I2 + Ib

Or why you don't try to use thevenin's theorem and replace R1 and R2 and Vcc with his equivalent circuit (Rth and Eth)?

How many loops do you have with KVL?

 

[Jony130]

Two loops:
First loop
Vcc = I1*R1 + I2*R2
And the second one
I2*R2 = ??

Or we can use nodal equation

(15V - Vb)/130k = Vb/150k + Ib

Where Ib = ??

Could Rb= Rb1||Rb2?

Yes, but what about Vcc ?

 

[Duave]

Two loops:
First loop
Vcc = I1*R1 + I2*R2
And the second one
I2*R2 = ??

Or we can use nodal equation

(15V - Vb)/130k = Vb/150k + Ib

Where Ib = ??Yes, but what about Vcc ?

I don't understand,

Wouldn't it be :

Vcc - Ib(R1||R2) - IeRe - Vbe = 0

and
Vcc = I1*R1 + I2*R2

 

[Jony130]

I don't understand,

Wouldn't it be :

Vcc - Ib(R1||R2) - IeRe - Vbe = 0

and
Vcc = I1*R1 + I2*R2

No this is incorrect because Ib current flows only through R1 resistor.
But we can use Rb = R1||R2 if you replace R1 and R2 voltage divider with his thevenin's equivalent circuit.

 

[berkeman]

...

Do *NOT* remove content from your posts. Check your PMs.

 

[Duave]

No this is incorrect because Ib current flows only through R1 resistor.
But we can use Rb = R1||R2 if you replace R1 and R2 voltage divider with his thevenin's equivalent circuit.

you please just tell me the KVL for this circuit again. I cannot obtain an official answer anywhere. I've been working on this problem for four days and it's only worth two points. I don't get it, and I need it to be laid out without anymore theory, on math.

You've been a big help. Could you show me both of the KVLs for this circuit

thank you

 

[Jony130]

Here you find the answer
https://www.physicsforums.com/showpost.php?p=4049964&postcount=17

Or use this nodal equation for Vb voltage

$\Large \frac{15 - Vb}{130} = \frac{Vb}{150} + \frac{\frac{Vb - 0.6}{7.5}}{101}$