Feedback? Vote!

I try, but I don't know the english technical terminations (or what the heck).

A transistor can be described as 2 gate(?). For example: 1'st gate: base-emitter, 2'nd gate: collector-emitter. There are network equations, for example:

u1=h11*i1+h12*u2
i2=h21*i1+h22*u2

This is the most common, but not the only way! It can be done with common base or common collector too! My 2'nd question: is there any reason to universally prefer one of these, instead of stereotype? I think there is a reason, why is it useful to use the appropiate one, when circuit can be analized simpler with it.

To be continued, actual example come soon!
 

forr

Member
2004-12-01 6:46 pm
Next door
Yes, 100 % feedback.

An emitter follower can be seen as an amplifiing device whose feedback input and output are the same.

And I think the not often explained zobel circuit used at the output of amplifiers using emitter followers (or compound pairs) is in fact a high frequency stabilisation component.

An amplifying circuit using apparently no feedback at all was published about two years ago in Electronics Word : it uses a simple common emitter without degeneration and and the load is a chain of diodes.
Distorsion is very small.

~~~~~~~~ Forr

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forr

Member
2004-12-01 6:46 pm
Next door
To VAD

The circuit was published by S. Chekcheyev in Circuit Ideas, Electronics World, july 2003, page 33. Here's a description :

Power supply : + 6 V
A 1 MOhm resistor from the power supply polarises the base of a BC547A.
The emitter of this transitor is connected to 0 V.
In the collector there is a chain of four either 1N4148 or BC547A connected as diodes (collector to base).
That's all.

Distorsion for 10 mV input when using the chain of the chain of BC547A : 0.0056%.
If the load would be a 110 Ohm resistor, the distorsion would be 0.96 %.
Voltage gain is said to be insensitive to power supply and temperature.

~~~~~~~ Forr

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