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Old 1st August 2002, 01:20 PM   #1
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Question my amp

what can you say about this sch?
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Old 1st August 2002, 01:36 PM   #2
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Hi shkal:
Interesting circuit. I am still trtying to untherstand some parts,
but, how do you will implement all these batteries ??

regards.
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Old 1st August 2002, 01:42 PM   #3
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Actually, batteries are LED's
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Old 1st August 2002, 06:06 PM   #4
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ok : batteries = leds.

Let me ask a question about imput circuit. When the signal produce an unbalance in the J1-J2 current, this, in turn, produce an unbalance in the Q1-Q2 current, right ?
The question is: what kind of circuit form Q1-Q2 ?(some cascode conection?).
Other point: why you take the reference of the current mirror Q6-Q7 from the output? what´s the idea ?

(Sorry if i bored you with many questions.)

Regards.
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Old 1st August 2002, 06:31 PM   #5
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Nothing like having a push-pull front end driving a
single-ended output stage.
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Old 1st August 2002, 08:12 PM   #6
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Default amplifier schematic

Hi Shkal,
As always I ask any solid reason not going for a completely complementary circuit?
Edgardo,
The input FET differential pair is cascoded with the bipolar transistor pair Q17 and Q18. The latter is <B><I>folded cascode</B></I> connected to Q1 and Q2.
These are loaded by a simple current mirror Q7 and Q8
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Old 1st August 2002, 08:52 PM   #7
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Thanks!, Elso.

Now, i wondering why Q7- Q8 current mirror are returned to the output node ?(i mean, Q11 colector).

Thanks again.
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Old 2nd August 2002, 06:06 AM   #8
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Question Amplifier Schematic

Hi Edgardo,
Yes that is kind of weird. I would connect it to the negative supply.
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Old 2nd August 2002, 10:46 AM   #9
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Using this "trick" I get almost constant voltage across C-E of Q8
at any output level. So
1) Early effect at Q8 canceled
2) Output resistance of Q8 stay constant

By this reasons, (and with little help from R25) nonlinear distortions greatly reduced.

Look at LT1468 and AD797 internal schematics

Sorry for my english
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Old 2nd August 2002, 01:37 PM   #10
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Ah..... Very nice!.

What about the circuit around M1... Is the same idea?. Keep the voltage across M1 constant, low the distortion, even in a follower?

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