Is it possible that the statement meant "if 100uV is applied between
the inverting and non-inverting terminals, the op-amp will go into
saturation"?

        If that was the question, then someone needs to explain negative
feedback :) Certainly, it's possible to use an op-amp to amplify a
differential signal between 50mV and 400mV. Just don't apply that difference
directly to the op-amp terminals.

        Perhaps the problem needs to be explained a little more. Is the
difference between two sensors being measured? or are there two sensors,
whose ouput varies between 50mV and 400mV? What is the amplified output
connected to? what range does the output voltage need to be in?


> -----Original Message-----
> From: Olin Lathrop [mailto:olin_piclist@EMBEDINC.COM]
> Sent: Wednesday, August 01, 2001 4:28 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [EE]
>
>
> > I am trying to use a CA3140E op-amp as a comparator.
> > The two inputs are chemical sensors. The difference voltage
> between them
> > can range between 400mV, to 50mV (100% concentration to 0%
> concentration).
> >
> > I remember reading somewhere in a text book, that if V1-V2
> is greater than
> > (I think) 100uV the op-amp will go into saturation.
> >
> > Can anyone a) clarify this for me, or b)suggest a better
> way to measure
> > the difference voltage.
>
> An opamp used as a comparator typically would go into
> saturation, especially
> since you probably want to add a little hysterisis.  A
> saturated opamp may
> take a little longer to respond to different input signals,
> but that should
> still be much faster than your chemical concentration can change.
>
>
> ********************************************************************
> Olin Lathrop, embedded systems consultant in Littleton Massachusetts
> (978) 742-9014, olin@embedinc.com, http://www.embedinc.com
>
> --
> http://www.piclist.com hint: The list server can filter out subtopics
> (like ads or off topics) for you. See http://www.piclist.com/#topics
>
>

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.