common collector amplifier
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
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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?
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See below links , please:
Common collector - Wikipedia, the free encyclopedia
http://users.ece.gatech.edu/~mleach/.../bjt/ccamp.pdf
http://www.ece.cmu.edu/~ee321/spring...lect15mar5.pdf
I hope these links can help you , read them and ask your questions if you can not understand them carefully.
Best Wishes
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
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 ?
No, I want to set the RI and RO , then calculate out the biasing resistor values.
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
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.
Follow below link :
http://www.seas.upenn.edu/~ese319/Le...Designs_09.pdf
By the way , with a simple approximation , we can say , that the current through R1 can be about 2ib and IR2 will be about ib.
Good luck
Goldsmith
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
Assume the Vcc=5V,
how to choose the Ieq /Icq ?
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)
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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,
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
http://www.cirvirlab.com/index.php/t...amplifier.html
and you can simulate it online:
http://www.cirvirlab.com/simulation/...ier_online.php