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Bootstrap this amplifier ?

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cartman007

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HI everyone.

I received this question to do.
My first question is, Is this an normal Emitter follower circuit when the output is take from the Collector?

Q1.png

Also what do they mean if they say I have to bootstrap this Amplifier without giving me any values for the components?

I dont understand the question.

Thanks
 


HI everyone.
I received this question to do.
My first question is, Is this an normal Emitter follower circuit when the output is take from the Collector?
View attachment 140100

Also what do they mean if they say I have to bootstrap this Amplifier without giving me any values for the components?

I dont understand the question.

Thanks

1.) No - it is NOT an emitter follower (in this case, the output would be at the emitter node).
2.) Do you know the meaning of the "bootstrap" method? This is a specific circuit modification for increasing the input impedance of the amplifier.
 

I presume, the exercise problem is referring to circuits that have been previously discussed in the lecture or text book. It's expecting you to turn back and review the respective chapter and design formulas.

I would expect a circuit as discussed in this chapter https://electronics.stackexchange.com/questions/268944/effect-of-bootstrapping-in-amplifier-circuit

I have been through the book a couple of times. Its "electronic devices 9th edition " But I can not find anything resembling that circuit.

@FvM
Yes I have seen a couple of Bootstrap circuits but I dont know how I am suppose to convert one to another?

I know that a cap would be feed back the output into the input and a resistor in applied just before the input signal but I can not see how I can convert it?
If I had some details on component values then sure I can keep currents etc the same.
 

I have been through the book a couple of times. Its "electronic devices 9th edition " But I can not find anything resembling that circuit.

@FvM
Yes I have seen a couple of Bootstrap circuits but I dont know how I am suppose to convert one to another?

I know that a cap would be feed back the output into the input and a resistor in applied just before the input signal but I can not see how I can convert it?
If I had some details on component values then sure I can keep currents etc the same.

Again my question: Do you know how bootstrap works?
Otherwise, you cannot design a corresponding circuit.
 

Again my question: Do you know how bootstrap works?
Otherwise, you cannot design a corresponding circuit.

It is to make a high impedance input by giving some positive feedback.
 

It is to make a high impedance input by giving some positive feedback.

OK - in principle, correct.
Can you draw a corresponding circuit modification?
What about gain requirements afer modification?
 

Ok soo some research that I have done before posting resulted in this circuit popping up allot.

This is the original Emitter Follower with bootstrapping applied.
bootstrap-emitter-follower.jpg

And because of my circuit I thought something like

bootstrap-emitter-follower-edit.png

The formula for resistor 3 is.

R3, = R3b = R3/ ( 1 - Ao )

But I dont have any values so I have no idea with what they want me to do.
 

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  • bootstrap-emitter-follower-edit.png
    bootstrap-emitter-follower-edit.png
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  • bootstrap-emitter-follower-edit.png
    bootstrap-emitter-follower-edit.png
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Last edited:

The circuit is useless due to missing emitter resistor. A meaningful circuit is shown in the post #2 link.
 

What about the output?

Does it also go to the Collector leg instead of the emitter as it was?

Thanks
 

I see exactly my circuit accept with a Re and the output on the collector.

But why would they tell me to convert one from the other?
It just seems more and more like they want me to just draw an entirely different circuit ?

Thanks
 

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