Hi all.

Please have a look at the two attachments.

The first one is a biasing circuit.
In this circuit, I have to find the value of Rb1.
I have calculated that value which turns out to be 46.24k ohms.
But, it seems to be wrong.
I can't understand what mistake I am making.
If that answer is wrong, please help me with the approach to find the right answer.



The second ,attachment consists of a CE BJT amplifier.
I need to find the collector current and Midband gain of the amplifier.
Please tell me the correct method to approach to find the collector current and midband gain and help me solve it.

Thanks.

 

Since this is 'Homework Help' you are expected to show your efforts so far. Show how you got the value 46.24k.
Use Ohm's Law to calculate the circuit voltages and currents.

 

Since this is 'Homework Help' you are expected to show your efforts so far. Show how you got the value 46.24k.
Use Ohm's Law to calculate the circuit voltages and currents.

Since, we know the value of Vb, Vcc and Rb2, I found the value of Rb1 using the voltage divider formula.

3.65=((12)(Rb1))/(105.8k+Rb1). I solved for Rb1 and found it to be 46.24k ohms.

 

Since this is 'Homework Help' you are expected to show your efforts so far. Show how you got the value 46.24k.
Use Ohm's Law to calculate the circuit voltages and currents.

Please, explain a bit more clearer.

Thanks.

 

You have forgotten about the base current. Rb2 provide a current for Rb1 but also the base current.
http://forum.allaboutcircuits.com/threads/transistor-base.81886/#post-585781
http://forum.allaboutcircuits.com/threads/emitter-bias-feedback-with-ree.74106/#post-520814

 

You have forgotten about the base current. Rb2 provide a current for Rb1 but also the base current.
http://forum.allaboutcircuits.com/threads/transistor-base.81886/#post-585781
http://forum.allaboutcircuits.com/threads/emitter-bias-feedback-with-ree.74106/#post-520814

How to calculate that current?
How to calculate the current through Rb1?
Could you please explain that in steps.

 

You're given the emitter current & the transistor gain. That's all you need to calculate the DC base current.

 

Hi all.

Please have a look at the two attachments.

The first one is a biasing circuit.
In this circuit, I have to find the value of Rb1.
I have calculated that value which turns out to be 46.24k ohms.
But, it seems to be wrong.
I can't understand what mistake I am making.
If that answer is wrong, please help me with the approach to find the right answer.



The second ,attachment consists of a CE BJT amplifier.
I need to find the collector current and Midband gain of the amplifier.
Please tell me the correct method to approach to find the collector current and midband gain and help me solve it.

Thanks.

When calculating the current through RB1 you need to subtract the base current from the current through RB2.

 

Thank you all. Got the answer!