[sdiy] LT1228 Lm13600 crap

[ASSI]

On Sonntag, 22. Mai 2005 03:56, René Schmitz wrote:
> I would guess the reason for this difference is that there is current
> stolen from going to the diffamp, which is used for the variable bias
> in the output stage.

Considering that it's a Wilson mirror, the only way to "steal" current 
would be an incorrectly sized transistor so that the base currents 
don't cancel. On the other hand, the results from Ian might indicate 
that the DUT generally showed bad matching. The Wilson mirror needs 
considerably more voltage headroom to work correctly. Low bias voltages 
or high common mode input is one of the applications where the CA3080 
can't be replaced. 

On Sonntag, 22. Mai 2005 04:07, harrybissell wrote:
> The NE5517 has a different arrangement of bias for the buffer... It
> might act differently

I've heard that before, but the data sheets are inconclusive on that 
point. The circuit in the LM13700 data sheet does not match the 
description in the same data sheet and I personally think that the 
arrangement is quite close (if not outright identical) to that shown in 
the NE5517 data sheet (which is copy&paste in most other respects). Do 
you have any (better) information on the buffer biasing?

On Sonntag, 22. Mai 2005 17:18, Ian Fritz wrote:
> Worth having a close look at.  Is the data sheet on line?

The Philips Datasheet is on their website, document number 939-750-10796 
(the partnumber search might be easier, but I'm not sure if it turns up 
an inactive part that the NE5517 now is).

> Looking at the 13700 vs the 13600
> schematics, it appears that they just erased Q3!  Do you think the
> current theft could be eliminated by tying the buffer input to the
> negative rail?  I'm not sure how simplified these schematics are.

As I said above, the LM13600/LM13700 schematics should certainly be 
taken with a grain of salt.


Achim.
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