HERE IS: published circuit of non-monotonic output driver

The schematic diagram of an output buffer which displays
non monotonicity (measured at low frequencies, for
example in a direct current I-V plot), is published in
the following paper:

    J. Petrovik et al, "A 300k-Circuit ASIC Logic Family",
    1990 International Solid State Circuits Conference,
    Digest of Technical Papers ("ISSCC-90"), pp. 88-89.

Figure 6 of that paper shows a remarkably clever output
driver circuit which compensates for process variations,
supply voltage variations, and temperature variations.
It performs this compensation better than any other circuit
I've ever seen. (Quiz: but there's a cost; find the
cost. Hint: it starts with the letter "p")

If you put this output buffer on your curve tracer
to measure the I-V curves, AND if you took more than
10 nanoseconds to move from one point on the curve
to another point (i.e. if the A/D converter inside
your curve tracer needs more than 10ns to settle),
then you would see the exact I-V curve that Arpad
Muranyi drew:

>
> *
> * *
> * * * * * * * * *
> *
> *
> *
>

The region where the slope of the I-V curve goes negative
(an incremental *negative resistance*, not usually felt to
be the greatest thing in the world to hook up to a
transmission line), is caused by the compensation circuitry.
As Arpad hypothesized, there is indeed feedback in this
output driver circuit. And, oh by the way, the circuit
is symmetric; it has negative resistance in both its
IOH-VOH curve and also in its IOL-VOL curve.

Take a look at Figure 6 of the paper. Better yet, put it
in your local SPICE simulator and simulate it "at speed"
(transient) and also simulate a DC transfer curve. Don't
believe me, I'm some random guy you've never met. Don't
believe this message, it's just phosphor dots dancing on
your CRT. Be self sufficient, try it yourself and
make up your own mind.

There are two $64,000 questions:

   1. Does anybody actually _use_ circuits like Figure 6
       in real products?

   2. When you run the thing at full speed (transient
       analysis), does it work OK?

Final remark: the authors of this paper were from
"IBM General Technology Division, Essex Junction,
Vermont, USA".

--Mark Johnson
Received on Fri Sep 1 17:32:39 1995