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Old 13th July 2005, 07:36 PM   #11
vAD is offline vAD  Russian Federation
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Quote:
Originally posted by darkfenriz
1st:yes
2nd:?
Hello! The resistor, is a feedback but then any amplifier has a feedback. (local or global)Speaker too a feedback through the ground.
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Old 13th July 2005, 08:36 PM   #12
forr is offline forr  France
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Default Feedback? Vote!

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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Old 13th July 2005, 09:16 PM   #13
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1: yes
2: not really,
but I guess many guys enjoy matrix maths with the version
u1=h11*i1+h12*u2
i2=h21*i1+h22*u2
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Old 13th July 2005, 09:38 PM   #14
vAD is offline vAD  Russian Federation
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Default Re: Feedback? Vote!

Quote:
Originally posted by forr
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.
Please. Where it can be seen.
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Old 14th July 2005, 12:03 PM   #15
forr is offline forr  France
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Default Re: Feedback? Vote!

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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Old 14th July 2005, 01:27 PM   #16
Jorge is offline Jorge  Brazil
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Default forr

I used such a circuit (diodes as collector load) in the mid 70's as an head amplifier for an Ortofon MC20 MC cartridge.
It had very low noise with a BF200 RF transistor.
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Old 14th July 2005, 04:41 PM   #17
vAD is offline vAD  Russian Federation
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Default forr

Many thanks.
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