What different are between 6T SRAM and 4T SRAM?

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nemolee

Joined: 28 Dec 2004
Posts: 148
Helped: 2

30 May 2005 14:15 4t sram

What different are between 6T SRAM and 4T SRAM?
Please compare according to area and power.
And what are their circuit?

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IanP

Joined: 05 Oct 2004
Posts: 6490
Helped: 1542
Location: West Coast

31 May 2005 1:32 Re: What different are between 6T SRAM and 4T SRAM?

Quote:

Different types of SRAM cells are based on the type of load used in the elementary inverter of the
flip-flop cell. There are currently three types of SRAM memory cells :
• The 4T cell (four NMOS transistors plus two poly load resistors)
• The 6T cell (six transistors—four NMOS transistors plus two PMOS transistors)
• The TFT cell (four NMOS transistors plus two loads called TFTs)

http://smithsonianchips.si.edu/ice/cd/MEMORY97/SEC08.PDF
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IanP

kwkam

Joined: 25 Feb 2002
Posts: 299
Helped: 15
Location: Somewhere on earth

31 May 2005 15:05 What different are between 6T SRAM and 4T SRAM?

6T SRAM is standard with 2 back to back inverter as latch and 2 pass gate transistor. 4T SRAM, the PMOS in the inverter replace by a poly resistor. Usually, 4T SRAM is smaller because it only need a single PWELL. The power consumption is depends on the speed but not the SRAM type.