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common collector amplifier

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xylon89del

xylon89del

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Hi,

I have read the text books regarding common collector amplifier. But, stil very confused.

Anyone can provide a step-by-step guidelines to design a good common collector amplifier?
 

Hello Dear xylon89del
It is simple . the common collector is an amplifier which amplify the current ( just) . and it's input impedance is very high and it's out impedance is very low . and it's frequency response is incredible .
Good luck
Goldsmith

---------- Post added at 17:59 ---------- Previous post was at 17:57 ----------

By the way , you can understand it's specifications , when you draw it's AC equivalent circuit . do you know ho to find AC equivalent circuit or internal AC circuit of a transistor?

---------- Post added at 18:01 ---------- Previous post was at 17:59 ----------

See below links , please:
Common collector - Wikipedia, the free encyclopedia
https://users.ece.gatech.edu/~mleach/ece3050/notes/bjt/ccamp.pdf
https://www.ece.cmu.edu/~ee321/spring99/LECT/lect15mar5.pdf

I hope these links can help you , read them and ask your questions if you can not understand them carefully.
Best Wishes
 

goldsmith said:
Hello Dear xylon89del
It is simple . the common collector is an amplifier which amplify the current ( just) . and it's input impedance is very high and it's out impedance is very low . and it's frequency response is incredible .
Good luck
Goldsmith

---------- Post added at 17:59 ---------- Previous post was at 17:57 ----------

By the way , you can understand it's specifications , when you draw it's AC equivalent circuit . do you know ho to find AC equivalent circuit or internal AC circuit of a transistor?

---------- Post added at 18:01 ---------- Previous post was at 17:59 ----------

See below links , please:
Common collector - Wikipedia, the free encyclopedia
https://users.ece.gatech.edu/~mleach/ece3050/notes/bjt/ccamp.pdf
https://www.ece.cmu.edu/~ee321/spring99/LECT/lect15mar5.pdf

I hope these links can help you , read them and ask your questions if you can not understand them carefully.
Best Wishes
Click to expand...

Hi dear Goldsmith,

I have checked through the documents, all the common collector require positive and negative supply voltage.

Is it possible for having only positive supply voltage?
As I am calculating the analysis without the negative supply voltage, the resistance I got is negative.
 

Why not ? usually , you will not need negative supply for class A amplifiers . but it is possible . but at common collector class AB amplifier we need simultaneous supply .
Wish You the best
Goldsmith
 

goldsmith said:
Why not ? usually , you will not need negative supply for class A amplifiers . but it is possible . but at common collector class AB amplifier we need simultaneous supply .
Wish You the best
Goldsmith
Click to expand...

The tutorial seems like doing analysis based on given resistance values.

I hope to find tutorial that shows how to find the resistance values based on specification.
 

By the way , what do you mean by that :"
As I am calculating the analysis without the negative supply voltage, the resistance I got is negative." ?


Ok i think you want calculate the RI and Ro and AV And Ai ? isn't it ?
 

goldsmith said:
By the way , what do you mean by that :"
As I am calculating the analysis without the negative supply voltage, the resistance I got is negative." ?


Ok i think you want calculate the RI and Ro and AV And Ai ? isn't it ?
Click to expand...

No, I want to set the RI and RO , then calculate out the biasing resistor values.
 

xylon89del said:
Hi,

I have read the text books regarding common collector amplifier. But, stil very confused.

Anyone can provide a step-by-step guidelines to design a good common collector amplifier?
Click to expand...

Also, Common Collector is know as "Emitter Follower", and for a reason; the Emitter basically follows the Base input voltage!

It is most often used to 'buffer' a preceding stage (maybe an oscillator or opamp) that has a higher impedance (like 1 K Ohm) , to say, a 50 Ohm output for connection to a BNC panel jack (to the outside world) as for video or even HF frequencies and into the VHF range.

Jim
 
Last edited:

RF_Jim said:
Also, Common Collector is know as "Emitter Follower", and for a reason; the Emitter basically follows the Base input voltage!

It is most often used to 'buffer' a preceding stage (maybe an oscillator or apamp) with a higher impedance output, to say, a 50 Ohm outut as to a BNC panel jack as for video or even HF frequencies into the VHF range.

Jim
Click to expand...

Hi, i understand wat is a common collector doing. What I need is a tutorial to calculate out the biasing resistance values from specifications like output impedance.
 

xylon89del said:
Hi, i understand wat is a common collector doing. What I need is a tutorial to calculate out the biasing resistance values from specifications like output impedance.
Click to expand...

Well, having in mind this is an 'Emitter Follower' that leaves the calculations of currents (as determined by the transistor Alpha, which is related to transistor's Beta) involving the Emitter with primary regard to the currents involved. This will also relate back to the input Z.

But first, I see goldsmith has a link to a resource, so before I go much further that should probably be reviewed next.

Jim
 

Last edited:

Hummm .
Ok i want to describe that how you can design a CC amp :
VRE=VCE=VCC/2 AV=RE/RE+re AI=AV*(Rin/RL) I1=2ib I2=ib Ri = R1 II R2 II beta (re+RE)
RO=RE II re+ ((R1 II R2 II RG)/Beta)

---------- Post added at 22:12 ---------- Previous post was at 22:09 ----------

So let's start by a simple CC amp design : Consider about AV= 1 ( approx ) . suppose that we want design a simple CC amp at class A , with below characteristics :
vo =5v p-p ( without THD) RL=2.2k
So , for first step , can you tell me that how much should be the value of VCC? if you tell it correct , we will go to next step .

Good luck
Goldsmith
 

goldsmith said:
Hummm .
Ok i want to describe that how you can design a CC amp :
VRE=VCE=VCC/2 AV=RE/RE+re AI=AV*(Rin/RL) I1=2ib I2=ib Ri = R1 II R2 II beta (re+RE)
RO=RE II re+ ((R1 II R2 II RG)/Beta)

---------- Post added at 22:12 ---------- Previous post was at 22:09 ----------

So let's start by a simple CC amp design : Consider about AV= 1 ( approx ) . suppose that we want design a simple CC amp at class A , with below characteristics :
vo =5v p-p ( without THD) RL=2.2k
So , for first step , can you tell me that how much should be the value of VCC? if you tell it correct , we will go to next step .

Good luck
Goldsmith
Click to expand...

Goldsmith,

Can you explain more on the biasing eg how to choose the Q-point?

Besides that, I am also curious, why when I increase the R1 and R2 till a limit, Vb will become very small, and the signal output is distorted.
 

Again Hi
At first step , don't forget that the transistor is a logarithmic friend! and you will see magic and fantastic behavior from that !!!! so enjoy from your friendship with transistors !

Any where , We have a law at class A amplifier design , that VCE should be about vcc/2 do you know why ? because we will need simultaneous out put voltage .
I want that you learn the steps of design . ok ?
If yes ! follow below things and try to think about them .
So , can you predict the value of VCC ?
Best Lucks
Goldsmith
 

Point is that you need to have input voltage that needs no further amplification. Common collector amplifier is there to amplify current.

More details on this you can find in
**broken link removed**
and you can simulate it online:

**broken link removed**
 

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