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Old 1st September 2013, 09:48 AM   #101
Bonsai is offline Bonsai  Taiwan
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Quote:
Originally Posted by AndrewT View Post
Is it possible to incorporate the sot23 pad layout for an SMD inside or alongside the pad layout of the through hole To92 device?
A GDS (or SDG) To92 pin out is the most common for jFETs. Only the the 2N devices gave the Source as the middle pin.
A sot23 is 1=S, 2=D, 3=G and pin3 is the one on the other side of the package. Surely we just rotate the smd 130degrees to align the pads of both packages.

If this is possible (it does not create any additional PCB area) then we can incorporate both SMD & To92 pads for every transistor location.
Andrew, yes for tH board this should not be a problem.
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Old 1st September 2013, 10:03 AM   #102
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Yes, this is exactly what I had in mind concerning layout. I like footprints for big 10uF output caps too!
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Old 13th September 2013, 07:25 AM   #103
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Keeping an eye on this project with interest.

What would be great is a small, low cost board that can be mounted on the back of the pot.
Click the image to open in full size.
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Old 13th September 2013, 09:42 AM   #104
Calvin is offline Calvin  Germany
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Hi,

a dimensioned Bonsai ready for layouting in either TH or SMD style, with suggestions about devices, power supply range, etc. had been shown in #12, #29 and finally #79.
Unfortunately though, it seems no one really read thoroughly and wasted a thought
And now the Bonsai has become a Borbely, a simple two JFET Buffer
BTW: with matched JFETs and spending the upper JFETs the same source resistors as the lower JFETs, the output cap could be omitted with alltogether.
You´re really a funny bunch, guys

jauu
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Old 13th September 2013, 11:26 AM   #105
Bonsai is offline Bonsai  Taiwan
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Guys, I already laid the board out. I will order this week 2 for testing.

I've written up an article as well, but can only publish after I test the board. ( gotta get it 100% right ya know!)

I will post up the layout and schema later tonight.

I designed it for an Alps RK27. The board measures 25mm x 48mm and sits on the Alps pot directly.
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Old 13th September 2013, 11:36 AM   #106
Bonsai is offline Bonsai  Taiwan
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Quote:
Originally Posted by Calvin View Post
Hi,

a dimensioned Bonsai ready for layouting in either TH or SMD style, with suggestions about devices, power supply range, etc. had been shown in #12, #29 and finally #79.
Unfortunately though, it seems no one really read thoroughly and wasted a thought
And now the Bonsai has become a Borbely, a simple two JFET Buffer
BTW: with matched JFETs and spending the upper JFETs the same source resistors as the lower JFETs, the output cap could be omitted with alltogether.
You´re really a funny bunch, guys

jauu
Calvin
Yes you are right Calvin, it is quite possible to get the offset very low. But the FETs need to be well matched - I think dual LSK489 would be good here but they are hard to get and without the cascode, you need low input capacitance. Other option is a trim pot, but I tried to avoid that.

This design does not need matched FETs because the lower FET sets the source current and is sized to fall below the worst case Idss

No originality claimed for the circuit (originally published in 1960s I believe) and indeed Borbely and Pass (B1buffer) are very good designs. Hopefully though, this one is very compact and uses a high quality pot. Sims indicate very low distortion, as reported by NP and EB.
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Last edited by Bonsai; 13th September 2013 at 11:40 AM.
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Old 13th September 2013, 11:38 AM   #107
Bonsai is offline Bonsai  Taiwan
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That's a nice pot Ranchu32.

Can you send me the link to the mouser data sheet page? Not promising, but I could do a second layout for that pot.
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Old 13th September 2013, 01:16 PM   #108
PMI is offline PMI  United States
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Quote:
Originally Posted by Calvin View Post
Unfortunately though, it seems no one really read thoroughly and wasted a thought
No at all, Calvin.
(nanos gigantum humeris insidentes)

Tschüß
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Old 13th September 2013, 02:42 PM   #109
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Quote:
Originally Posted by Bonsai View Post

I designed it for an Alps RK27. The board measures 25mm x 48mm and sits on the Alps pot directly.
Yeah!
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Old 13th September 2013, 08:53 PM   #110
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Quote:
Originally Posted by Bonsai View Post
That's a nice pot Ranchu32.

Can you send me the link to the mouser data sheet page? Not promising, but I could do a second layout for that pot.
Here's the link Bonsai: RK09L12D0A1T ALPS | Mouser

But the way you have designed it for the RK27 is even better!
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