[sdiy] Three-ball OTA

[KD KD]

Dear singularity!

Ah, yes! Mr . Zumchak who did the Moog Sonic six. 3 and 4 legged NPN,PNP
and NPN/PNP current mirrors do exist from Rhom and NXP notably.

You could be sucking out to much current so you probably saturate the
whole hoopla.(disclaimer, without having seen your
cirquit).(disclaimer 2: i'm just a gardener, knows
nothing about EE).

Im Denny Crane..Mr Crane!

http://24.media.tumblr.com/tumblr_l6vxbiVIeP1qcfx9xo1_500.jpg

2011/9/23, Rutger Vlek <rutgervlek at gmail.com>:
> Dear all,
> Inspired by this (http://www.uni-bonn.de/~uzs159/ota3080.html) comprehensive
> explanation of an OTA, I have been playing around with an OTA modelled in
> Spice. Towards the end of the article a "three-ball" OTA is proposed,
> effectively leaving out one current mirror (the one that deals with the
> control current Iabc). Instead the article proposes to "suck out" current
> from the NPN differential pair directly with a NPN transistor.

> This idea of a three-ball OTA seemed to make sense at first and performed
> well in simulation when I "sucked" current out of the differential pair with
> a simulated current source. However, as soon as I replaced the simulated
> current source with a more reallistic NPN expo convertor, distortion
> characteristics went up (in the wrong direction) tremendously. I'm having a
> hard time understanding this behaviour. Anyone willing to explain it to me?
>
> Regards,
>
> Rutger
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