SRAM and Flip-Flops
Hello all. Thanks for taking up your time to read my post.
Still learning, but this question is bugging me. I finally sort of understand how Flip-Flops work in 74LCX16821MTDX as the datasheet of http://www.kynix.com/uploadfiles/pdf/74LCX16821MTDX.pdf, and how that is used to maintain Shift Registers and such.
From the wiki page: "Each bit in an SRAM is stored on four transistors"
Why four? SRAM is a series of Latches (or flip-flops) correct?......flip-flops only have two Transistors correct? Unless I'm confused which i might be?
I've seen the schematic of a Flip-Flop of course (using NAND gates and such)? But NAND gates take more than one transistor to build yet i've seen sample Flip-Flops (Using LEDS) with just 2 Transistors?
As you can tell I'm a bit confused. SRAM is saying it needs 4 Transistors to store a bit......yet i've seen 2 Transistors store a state (which I guess could be considered a bit), and NAND gate flip flops (which surely take more than 1 transistors to make a NAND gate?
I'm thinking of normal Bi-polar junction Transistors however, and upon further reading it appears "Most" SRAM uses FET's....would that have any difference however in how they are constructed ?
Can anyone help me ? I am very puzzled about this question.
Added 8 years, 1 month ago.
2 Answers
If you're using BJT's and resistors, yes flipflops are 2 transistors.
In a modern CMOS process (FETs) resistors are difficult so they're often replaced by transistors. Also SRAM is made with D-latches not SR-latches.
The wikipedia page has more: https://en.wikipedia.org/wiki/Static_random-access_memory#Design
I'd also recommend searching for the differences between d-latches SR 'flops and JK 'flops. Also noting that some are synchronous ("have a clock") and some are not. This should give you a fuller picture of memory types.
Answered 8 years, 1 month ago.
thanks for your reply. I will take a thorough look at the wikipedia. thanks a lot.
Answered 8 years, 1 month ago.