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Old 3rd January 2012, 01:42 AM   #1
OH5Z is offline OH5Z  Finland
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Default What is sucking in this wiring?

How about that Q2?
Can it be pnp?
Has emitter and collector to be changed?
And how about C4 value?
Click the image to open in full size.
Thanks!
Z
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Old 3rd January 2012, 03:04 AM   #2
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Better go for better designs.

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Old 3rd January 2012, 05:45 AM   #3
Nrik is offline Nrik  Denmark
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Agree on that. For simple, safe and good sounding stuff, Look at DestroyerX ( Carlos') DX amplifier : http://users.tpg.com.au/users/gerskine/dxamp/
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Old 3rd January 2012, 12:30 PM   #4
djk is online now djk
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There is nothing really wrong with that design at all.

"How about that Q2?"

What about it, it's one have of the diff input pair.

"Can it be pnp?"

It must be the same as Q1, it's one half of the diff input pair.

"Has emitter and collector to be changed?"

No, it's one half of the diff input pair.

"And how about C4 value?"

47F~100F would be a good value, with R8 and R9 it's part of the bootstrap CCS for Q3.

R2 bootstraps the input impedance (makes it higher).

This is really a common and ordinary amplifier. Use a 10Ω+0.1F Zobel on the output to ground (before the fuse).
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Old 6th January 2012, 06:28 AM   #5
OH5Z is offline OH5Z  Finland
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HI!
Thanks for advice.
Now I'm wondering Q1. Where comes its collector current?
I draw the schematic so that positive side is upper and it's now easier to understand, but Q1 seems to be quite weird on ordinary differential amp.

J
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Old 6th January 2012, 06:55 AM   #6
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Quote:
Originally Posted by OH5Z View Post
Now I'm wondering Q1. Where comes its collector current? J
R5 & Base Emmiter of Q3
Doc
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Old 6th January 2012, 07:13 AM   #7
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DJK you are right, there is nothing wrong with the design, it is just not drawn nicely that is all. The person who drew the schematic forgot to put a ground connection between the 4700uF power supply caps.
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Old 6th January 2012, 02:08 PM   #8
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almost class B ... no thermal compensation .... thermal run away is waiting around the corner ...if pushed it will fail .... at 42+42 volts i will be pushed any way
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Old 6th January 2012, 11:03 PM   #9
djk is online now djk
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It's class AB+B.

Adjust R1 to about 0.34V across the base of each output.

Attach D4, D5 to the heatsink for the drivers (if any).
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Old 7th January 2012, 02:08 AM   #10
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that IS the most bizarre way i've seen a diff amp drawn. this looks like something designed for a cheap guitar amp or a console "hi-fi" in the 70's.

btw Q4 in the above schematic is the constant current source for the diff amp. the diodes D4, D5 should be attached to the heat sink for thermal stability.

as for odd ways of drawing diff amps, i always thought the way they were drawn in some of National Semiconductor's data sheets was rather strange.
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File Type: jpg natsemi-diff.jpg (12.7 KB, 91 views)
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