[Goobley]

I've spent a fair amount of time over the past week running various simulations with regards to constructing such a buffer with no output blocking caps and I have to say that I'm struggling due to the threshold voltage of mosfets - I haven't got a vbe multiplier to work properly yet.
I chose mosfets as I want a high Zi.
I'm gonna keep at it, but if anyone knows how to design such a thing I'd be grateful for a few pointers.
 
The other idea that I've had is to build a class A source follower and use a dc servo, is this feasible?
 
Any ideas on how to build a high Zi buffer that has no offset would be very welcome,
 
Cheers,
CHris

 

[kevin gilmore]

lookup the satri circuit which is usually 2 jfets and 2 more jfets, or bipolar, or mosfets.

 

[Avro_Arrow]

Quote:

lookup the satri circuit which is usually 2 jfets and 2 more jfets, or bipolar, or mosfets.

Like this?
 
 

 

[Goobley]

If I were to cut that schematic in half, just before the LEDs and then take the output side, would that be completely idiotic? I simulated it in TINA using BC550/BC560 and if I'm shocked to say that, at 1kHz there's an input impedance of about 6Mohm which seemed surprisingly high, i thought that this was impossibly high for BJTs, so tell me then, where have I screwed up?
 
If i didn't get it wrong then this looks pretty brilliant.
Thanks for your help,

 

[kevin gilmore]

http://www.diyaudio.com/forums/analogue-source/154210-mpp-266.html#post2699945
 
just the first stage.

 

[Avro_Arrow]

Quote:

http://www.diyaudio.com/forums/analogue-source/154210-mpp-266.html#post2699945
 
just the first stage.

Hey, I drew the schematic in post 2654!
 
My how things get around...

 

[dsavitsk]

Look here, too http://diy.ecpaudio.com/2012/11/black-diamond-headphone-amplifier-part-1.html

Part 2, which I hope to post sooner than later, uses JFETs on the input. Replacing the output devices with FETs is trivial.

 

[Steve Eddy]

Or just watch the film Dr. Strangelove or: How I Learned to Stop Worrying and Love the Blocking Cap.

 
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