DIY CMOS RAM Memory

If you have seen my other instructable on ram memory, you probably know that I used transistors to make a register. In this instructable I will show you how to make a register using CMOS gates.

If you haven't seen my other instructable, check it out http://www.instructables.com/id/DIY-RAM-Memory-Register-Style/

Step 1: What is CMOS?

CMOS stands for Complementary Metal Oxide Semiconductors.  Its a form of logic that uses very little current and requires no resistors.  It uses MOSFETs in a complementary arrangement, so you use a P-channel and an N-channel MOSFET at one time.  The cool thing about CMOS is that when one MOSFET is on, the other is off, so gates don't use very much current. Another thing about MOSFETs is that the gate is not connected in any way to the drain or source so it requires no resistor, unlike ordinary bipolar transistors.

Comments

[nancyjohns]

How do you program it? I think its really cool.

[WakeUpWolfgang]

I am looking for a schematic so I can make my own ssd even if it is 1 to 8 bits big. Where could I find one or an instructable. I want it to remember the bits even with no power.

[Teslaling]

The problem with an electronic circuit that remembers its data when the power is lost is that it requires a floating-gate transistor. Floating-gate transistors have a gate, source and drain like regular fets, but there is also a second gate that isn't connected to anything, hence it's floating. Putting a large charge on the gate will put a small charge on the floating gate, just enough to turn on the transistor. Then a large charge of the opposite polarity on the gate to remove the charge on the floating gate. The best option you would have is a really big capacitor on the gate and a transmission gate between the transistor-capacitor pair and the rest of the circuit. It won't be permanent, but it will last for a long time (depending on the size of the capacitor.)

[WakeUpWolfgang]

So is that how it works in a flash drive and a ssd and there is no permanent soultion? I am planing on making a computer from scrach and making my own parts this is the only part i am having trubbles with. sry for bad spelling i dont have spell check on my tablit

[MattTheGeek]

it's Incredible how far we have gotten in electronics and semiconductors. Great instructable.

[Goodhart]

I have GOT to find that article I had (it was an April Fools article in an electronics magazine) that showed how to construct a one BIT memory with tubes......foot print, about the length and width of an large encyclopedia, and the height off the table, about 14 inches. :-) It worked too, if you could find a USE for a single BIT LOL

[Teslaling]

THATS AWESOME!!!!!!!!! I would so build it (or maybe 8)!!!

[Goodhart]

So far, I haven't found the schematic nor the plans, in hard copy nor on line, the closest thing I have found so far is the WOM (write only memory) :-)

[tinker234]

hey is this computer memory and could i make a 16 trigbyte hard drive

[Teslaling]

Technically yes, it is computer memory, but it is ram, not a hard drive. A hard drive saves memory even when it loses power, this will lose its data after the power is removed.

And as takide said, it would take trillions of transistors.

[tinker234]

ok thanks so i could

[Teslaling]

Yeah if you really want to...

[tinker234]

so hey could i put a cell phone battery on board to power it alll the time

[Teslaling]

Haha!!! The next solid state drive, and its easier than ever to clean up your hard drive, just disconnect all power!!!

[tinker234]

i know but im talking about using a cell phone bTTERY TO POWER IT WHENM THE COMPUTER IS OFF

[Teslaling]

Yeah, i understood that, but the first thing i thought of was a sales gimmick thing. You could use a phone battery to keep power, just make sure that it can be recharged in circuit, and can go for a while in between charges.

[tinker234]

yaha i know hey what about the power always powering the circut but the cell phone battery in case of blackout

[Teslaling]

That would definitely be a much more secure way to do it.

[tinker234]

i know

[takide]

you could do it though....

[takide]

you would need TRILLIONS of transistors dude, thats why most computer ram systems are put into microchips so that they can cram TONS of transistors into a chip, thus storing your data.

[tinker234]

ok how do i do that

[mnova]

What should my input voltage be?

[Teslaling]

It really depends on your transistors, but 3.3v to 5v should work. 5v will almost definately work, 3.3v might work. I would not reccomend going over 5v because most small signal msofets have a gate voltage of 5v

[mnova]

I used 4.5 volts (3 AAA) batteries, BS170 for the N-channel MOSFETS and zvp2106a for the P-channel MOSFETS. . . . . I actually heard the circuit fry. -_-

[Teslaling]

Thats not good!! My guess is that a few of your transistors are backwards. The BS170 has a reverse voltage diode in it (which shorts if the transistor is backwards) that will fry if you put too much current thru it. 3 AAA's is definitely enough to fry the transistors.

The Datasheet for the ZVP2106A didn't say whether or not it has a diode in it, but be cautious and check your circuit.

Good luck!!!

[laserjocky]

Wow this gives me some renewed appreciation for RAM... I've got a few billion of these little puppies sitting beneath my fingertips at the moment. Incredible.

[gamini]

Thanks for this .

Can I save some of my information ?

[parukboy]

This looks very similar to a negative edge flip flop

[Teslaling]

Thats because it IS very similar. The main differences are that this is a latch not a flip flop, and that it is positive edge triggered!

[elias.alberto]

Any tests on the frequency you can achieve with this? (i'm not thinking of any practical use, I'm just curious)

[Teslaling]

No tests, but the MOSFETs are rated at a few MHz so it should be fast...in theory...

[pyrohaz]

I think the main limiter of frequency for this would be the capacitance of the breadboard its self, i managed to get about 60khz out of a 555 timer cleanly driving a mosfet, remembering that if a mosfet isnt driven properly, it heats up due to being stuck between cut off and saturation :) Crossing wires also add capacitance.

[Teslaling]

I didn't think of that, but it would definitely play a factor in speed. Thanks for that information.

[Thereyouhaveit]

Woah , good start for you .
Who knows , you might join a big shot company dealing in memory and taking care of the ... 10nm process ? ;)

[Geosync]

Thanks for the excellent demo. It's a great reminder of what VLSI chips comprise. I see the beginnings of a real iPod killer here. All you need is more CMOS and an acre (or two) of land to wire them on.

[Teslaling]

What would we call it? The iPod MEGA?!?!

[riodoro1]

i guess it is 4 bits that gives you 1 byte.

[Teslaling]

No, its 8 bits in a byte... yeah its a bit strange

[Loukin]

What is the capacity on this ram?