SV: Re: [sdiy] CEM3328 seems to only have buffers at the end

[René Schmitz]

Hi Antti, Jürgen and all,

>> And with the buffers clipping themselves, unsymmetrically as
>> in the 2040 even, you have that wonderful interaction of frequency
>> depended differential pair distortion (around the cutoff frequency,
>> as you explained), and the frequency independend, but somehow
>> transient depended, distortion from the buffers.
> 
> 
> I _think_ (read: I've done a few spice simulations but nothing 
> conclusive) what happens here is that the base-collector diode becomes 
> active when capacitor voltage goes below diff-pair - input. This is 
> somewhat similar to tube amplifiers where the grid also acts as a diode 
> thus varying the DC voltage over the interstage DC blocking capacitor.

I think that it is because of the limited compliance of the "single 
ball" OTA structure. It can source to V+ but sink only to the emitter 
potential + Vcesat. Thus with large signals a bias across the cap develops.

Cheers,
  René

-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159