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Old 4th January 2004, 09:34 PM   #1
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Default my latest amplifer

I thought I'd share my latest almost finnished amp with all.

It's basicly a p3a front-end with constant current instead of the boot strap and then into a tip122 quasi output but at a lower voltage so I could use 2n390X throught out.

It was made with parts on hand so some values are less then optimum like the 33p cap in the front-end should of been larger.
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Old 4th January 2004, 09:47 PM   #2
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Default Shcematic

Here's the shcematic.
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Old 4th January 2004, 10:03 PM   #3
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it looks good.

one observation: since you alread have the ccs there, why don't you just add one transistor so that the input stage also has a ccs?
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Old 4th January 2004, 10:44 PM   #4
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Good point, I don't know.

I have the student version of pspice so 10 bjt or less but I could of done the front end seperate from the rest to work out genral values and soft analisys.

I think I'll revise.

Thanks
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Old 4th January 2004, 11:24 PM   #5
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Arrow Reply

u can use Circuitmaker Student edition for 50 device limitation
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Old 5th January 2004, 12:02 AM   #6
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by the way, what does R18 (220ohm) do for you?
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Old 5th January 2004, 01:15 AM   #7
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Quote:
by the way, what does R18 (220ohm) do for you?
I only had a 500 ohm pot on hand and this would not work. So I added the 220 ohm r to get me into the 500~700 ohm range which would get me a fair amount of offset control and get the A class vas to work properly.
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Old 5th January 2004, 01:22 AM   #8
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but isn't it shorted by the wiper? maybe you wanted to put it above the trimmer, depending on the desired value of the resistor / trimmer combination.
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Old 5th January 2004, 02:08 AM   #9
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r18 is on the otherside of the trimmer, it's just a typo I made recreating the circuit in eagle to post online.
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Old 5th January 2004, 03:48 AM   #10
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Default Revision

Here's the reivsed.

I like to to keep simple things simple, but Millwood if your reading, do you think by using a shared ccs in the df stage I will be introducing more noise by the flucutuations caused by the vas, than I can wrinkle out by the increased gain of the new df's ccs vs negative feedback?

I have one made already, I'll make another with the revisions and see which looks good.
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