Unity gain solid state buffer
 

Hi!

In these relatively quiet days around xmas. I've conceived the unity gain buffer depicted here below.

https://lh4.googleusercontent.com/-e...Buffer-DEF.png

Questions is: have you yet seen some similar circuit in the past? (also not in the audio electronic field). If the answer is "yes" can you tell me vhere you seen it and from what author?

Thanks in advance
Piercarlo

For who want to try out the schematic proposed above here below will find a track layout for build it on a small PCB, or better again, on a breadboard. BF245A (or BF245B with an Idss below 3 mA) may be replaced with any similar N channel device with an Idss comprised between 1 to 3 mA, The JFET is used in layout with swapped source and drain (operation possible with the most of general purpose JFETs) just because more straightforward to accomodate.

https://lh6.googleusercontent.com/-g...r-PCBTRACK.png

Happy New Year! :).

Piercarlo

Revised - Suppression of a ground loop.

https://lh5.googleusercontent.com/-q...ferPCB-RV2.png

Happy New Year - Again! :).

Piercarlo

I've never seen this, it is unique, congratulations!

Hugh

Thanks! :-) In the next days I'll mount a pair of them for practical testing and for my use (I'm building a small integrated for headphone, in pair with a class A power amplifier derived from JLH 1969, that i named "JLH2012"). Stay tuned! ;-)

Piercarlo

This topology could be a good upgrade (front-end) for Andrea Cioffoli's Power Follower 99 - go to
http://www.audiodesignguide.com/my/Follower_99c.gif
http://www.diyaudio.com/forums/solid...pressions.html
http://www.diyaudio.com/forums/pass-...9c-vs-zen.html

Whats is good or special or different with regard to the performance to warrant so much complexity for just a buffer ?? It must have THD 120db below on heavy loads , extreme speed or PSRR ??.... when we can come close to that performance by using just 4 transitors and less than 1/3 the passives. Coupling caps are not well regarded in audio world either.

Who's care of these "questions"? If I wish i can replace all just with a single op-amp connected as voltage follower... If I don't try so is because i wan't try something of different. I CAN do it and I DO it! :-)

Piercarlo

Your circuit looks similar to Maxim's BB3553 or LH0063 (used to be Burr Brown before).
http://www.datasheetcatalog.org/data.../493512_DS.pdf
These are not monolithic IC but thickfilm hybrid inside.

Before getting too involved with PCB design etc., have you made a lash-up prototype of this to make sure it all works as expected? I only mention it because spice simulations normally assume that all transistors are perfectly matched clones of one another and are closely thermally linked. In fact that all components are 'perfect'. Unless you deliberately put in variations that are more like real world scenarios. (?)

Just a thought....