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From: mark@mips.com (Mark G. Johnson)
Newsgroups: sci.electronics,misc.wanted
Subject: Re: Looking for values of C for DRAM memory elements
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Date: 17 Mar 91 17:59:37 GMT
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In article <91075.114646IO80900@MAINE.BITNET> IO80900@MAINE.BITNET writes:
  >For a project that I am working on, I need to know the capacitances of
  >"typical" DRAM cells in use today (1-T).

The best place to look is in the back issued of the IEEE Journal of
Solid State Circuits; the October issues are about memory devices.
Here's an excerpt:

  "Cell size is 4.0 x 9.0 microns, and the layout is shown in Figure
   2.   In this layout, the storage capacitor comprises 29 percent
   of the cell area, giving a cell capacitance of 32fF when a "1" is
   stored, and 35 fF when a "0" is stored.  Differential signal at
   the sense amplifier is approximately 80-90 mV with Vcc=4.5V ..."

          ---- R. Taylor and M. Johnson, "A 1-Mbit CMOS Dynamic RAM
               with a Divided Bitline Matrix Architecture," IEEE
               Journal of Solid State Circuits, Vol SC-20, No.5,
               October 1985, pp. 894-902.


For those who wondered: Yes, the cell capacitance is indeed nonlinear and
varies with stored voltage.  There is after all a PN junction involved.
-- 
 -- Mark Johnson	
 	MIPS Computer Systems, 930 E. Arques M/S 2-02, Sunnyvale, CA 94086
	(408) 524-8308    mark@mips.com  {or ...!decwrl!mips!mark}