Re: New input stage

From: sleeper75se (sleeper75se_at_yahoo.se)
Date: 2002-01-11 02:05:56


--- In buildcheapeeg_at_yahoogroups.com, "Joerg Hansmann" <info_at_jhansmann.de> wrote:
> Hi,
>
> ----- Original Message -----
> From: sleeper75se <sleeper75se_at_yahoo.se>
> To: <buildcheapeeg_at_yahoogroups.com>
> Sent: Thursday, January 10, 2002 9:16 AM
> Subject: [buildcheapeeg] Re: New input stage
>
>
> > Hi Jim, Joerg and all.
> >
> > I've updated the input stage schematic a bit, so now it is more
> > flexible. New version is in the files-section.
> ...
> [many improvements]
>
> I have done a simulation (see attachment, SWCAD3 simulation source
> included) on the supply decoupling network and have some questions:
>
> You get heavy voltage drop on the 220 Ohms resistors.
> To meet the minimum supply voltage of the LT1167 of +-2.3 V
> you would have to use a voltage supply that has greater equal
> +-3.8 V.
>
> In the AC-simulation the supply decoupling network has only
> moderate effect above 2kHz. Below 2 kHz it has 0dB attenuation.
>
> Why are you not using a star formation to a low impedance source
> instead of this ladder formation ?
>

Hi Joerg,

I have to confess, I'm getting confused...
what is best? Star or bus? I'm a newbie in this territory...
previously 100nF (or 10nF sometimes) close to the IC's + a
large "reservoir" capacitor of 10-100uF has been enough in my
projects. But those designs were never low-noise/low-amplitude
circuits.

Putting in three 220 ohms resistors in series, without doing any
calculations, was a bit sloppy on my part, I just took a part that
was used elsewhere :-p - thanks for checking that out!

I suppose there is a difference in approach here. You propose a
strictly low-voltage approach while Jim suggests high-voltage (where
the voltage drop is less important). Is there a middle way here that
lets people choose which ever way they feel most comfortable with?
I want the design to be as flexible as possible, so that people can
adapt it to their specific needs. Star ground with 220 ohm resistors?
Bus structure with 47 ohm resistors?

Regards,

Andreas



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