Subject: Re: Nonmonotonic Pulldown I-V curves

From: Barry Katz <[email-masked]>
Date: Wed, 20 Apr 94 09:40:51 EDT

After further review of Jon's report and some addition experimentation
on my part I think I may have identified a problem with the presented
results.

In my experiments, I found that the bulk currents were on the order of
picoAmps and that the difference on the order of femptoAmps. This
leads me to believe that the currents shown in Figure 5 of the report
are in fact the parasitic diode currents not the transistor Bulk
currents. This may just be a terminology issue.

However, something does appears to be inconsistent because even if we
were talking about diode currents the difference in these diode
currents should still be zero. This is based on the fact the the
transistor bulk currents are effectively zero and the current through
the diode is voltage dependent. Therefore, since both the "on" and
"off" cases have the same sweep, the difference between the currents
for these cases will be zero. This is regardless of your definition of
i_bulk.

Comments anyone?

Jon, can you put the spice decks corresponding to your report on the
reflector? 

Barry-

My test structure is shown below.

                 i_drain                   ---------
             <---                          |       |
          ---------------------------------|Ammeter| SWEEP
          |                  |             |       |
          |                  |  |i_clamp   ---------
          |                  |  |              |
 i_g   ----    i_bulk       --- V              |
 --> | |     <---            ^                 |
   --| | |--------          / \                |
   | | |         |          ---                |
  / \  ----      |           |                 |
 ( + )    | |    |           |                 |
 ( - )    | |i_s |           |                 |
  \ /     | V    |           |                 |
   |      |      |           |                 |
  ---    ---    ---         ---               ---
   -      -      -           -                 -

I think Jon's test structure was as follows

                                i_drain    ---------
                               <---        |       |
          ---------------------------------|Ammeter| SWEEP
          |                  |             |       |
          |                  |  |i_clamp   ---------
          |                  |  |              |
 i_g   ----                 --- V              |
 --> | |                     ^                 |
   --| | |--------          / \                |
   | | |         |          ---                |
  / \  ----      |           |                 |
 ( + )    | |    ------------|                 |
 ( - )    | |i_s          -------  |           |
  \ /     | V            |Ammeter| | i_bulk    |
   |      |               -------  V           |
  ---    ---                 |                ---
   -      -                 ---                -
                             -

---

From: [email-masked] (Jon Powell)
Date: Wed, 20 Apr 94 09:47:10 PDT

If I understand your drawing correctly it does not properly reflect
my test structure.

My test circuit is as shown in Figure 1 and 2 of the memo. There was
no clamp diode, just one CMOS transistor. We simulated bulk current
(Ib) (as shown) in the Amp range.

jonp