Spacewar! (was Re: Laser display...)

[Scott Stevens]

On Sun, 20 Feb 2005 20:40:08 -0500 (EST)
der Mouse <mouse at rodents.montreal.qc.ca> wrote:

> > If you look at these circuits, you will find they are amplifiers
> > that are driven in to clipping [...]
> 
> > The point of this rambling, as some have pointed out before, is that
> > the circuit is the same, it is the mode of operation that differs.
> 
> The circuit is fundamentally the same, but the details are vastly
> different.  An amplifier designed for analog amplification will be
> tuned for linearity in the non-clipping region and designed to operate
> there.  An amplifier designed for use as a logic gate will be tuned
> for operation in the saturated/cutoff regions and not particularly
> interested in linearity in the non-clipping region (and indeed it
> wouldn't surprise me to see such a thing exceed its design current
> draw and heat dissipation parameters if operated in the "linear"
> region).
> 
> > (and yes, you can build useable audio amps out of 4000 series
> > inverters).
> 
> I'm surprised they're linear enough.  Or are you just designing under
> the assumption of infinite gain, depending on negative feedback to
> linearize things?
> 

Yes.  You bias them into a linear region with a feedback resistor
between input and output.  It works, but you're better off using a
regular op-amp, unless you already have sections of an inverter 'sitting
around' to use up.  It's a crude audio amp you end up with.

-Scott