Isn't this just a flip flop?
Almost. It's a gated D latch, which is level sensitive and behaves asynchronously, as opposed to a D flip flop, which is an edge sensitive primitive.
How to Build 1 Bit of RAM Using Transistors
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Re: How to Build 1 Bit of RAM Using Transistors
#12Isn't this just a flip flop?
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Re: How to Build 1 Bit of RAM Using Transistors
#13Re: How to Build 1 Bit of RAM Using Transistors
#14A capacitor is 1 bit of memory.
Yes, but that's different.
A simple capacitor does not require an external power supply to store the state, but the state decays in time.
A flip-flop requires an external supply to store the state, but the state is stable indefinitely.
Re: How to Build 1 Bit of RAM Using Transistors
#15If you are a software person looking to learn a few more things about electronics I recommend the videos of Ben Eater on you tube.
Here is one that he explains the SR latch: https://www.youtube.com/watch?v=KM0DdEaY5sY
Also the lectures by this amazing MIT professor: https://www.youtube.com/watch?v=AfQxyVuLeCs
Re: How to Build 1 Bit of RAM Using Transistors
#16I've always wondered why most people seem to draw flip-flops with the crossed wires and both gates pointing the same way, when I think this representation makes it far clearer:
https://i.imgur.com/cwZe7Zf.png
When both inputs are low, the NORs are equivalent to NOTs and you can see they form a storage loop. When one input is high, it forces the loop into the corresponding state.
That said, I'm disappointed this article doesn't show the transistor-level schematic, because trying to read from a breadboard is extremely difficult.
Re: How to Build 1 Bit of RAM Using Transistors
#17I once made a single-transistor latch by accident. It acted as a single bit of memory and retained its value for weeks until I got bored with the project. I had been making magnetic snap-together circuits, so I had a bunch of small PCBs with simple 2- and 3-pin footprints and holes that I soldered neodymium disc magnets into. I put a big TO-220 N-fet on one of them, and stuck it to a laminated whiteboard so that the…
I think you just made a single bit of DRAM. It's surprising how long charges can stay around given suitably dry climate and insulators, and LEDs don't require a lot of power to light up either. A TO-220 package suggests a power transistor, so it will have substantially more gate capacitance than a typical logic-level one.
Re: How to Build 1 Bit of RAM Using Transistors
#18I've always wondered why most people seem to draw flip-flops with the crossed wires and both gates pointing the same way, when I think this representation makes it far clearer: https://i.imgur.com/cwZe7Zf.png When both inputs are low, the NORs are equivalent to NOTs and you can see they form a storage loop. When one input is high, it forces the loop into the corresponding state. That said, I'm disappointed this artic…
Because if you have an input on the right and you combine this with other digital logic you are going to end up with crossed wires backtracking to that input on the right somewhere, I would guess.
Re: How to Build 1 Bit of RAM Using Transistors
#19I've always wondered why most people seem to draw flip-flops with the crossed wires and both gates pointing the same way, when I think this representation makes it far clearer: https://i.imgur.com/cwZe7Zf.png When both inputs are low, the NORs are equivalent to NOTs and you can see they form a storage loop. When one input is high, it forces the loop into the corresponding state. That said, I'm disappointed this artic…
The reason it is not usually drawn that way is it is a cardinal sin to draw logic gates 'backward' on a logic schematic. It is a schematic schematic equivalent of 'goto' and makes schematics confusing to follow. For a simple inverter in a flipflop it isn't so bad, but when you are inside of a larger schematic it is better to stick with the best practice of signals flowing left to right for all symbols.
PS - For what its worth, that image has a transparent background, so when the imgur viewer displays it you get black traces on a black background.
Re: How to Build 1 Bit of RAM Using Transistors
#20I've always wondered why most people seem to draw flip-flops with the crossed wires and both gates pointing the same way, when I think this representation makes it far clearer: https://i.imgur.com/cwZe7Zf.png When both inputs are low, the NORs are equivalent to NOTs and you can see they form a storage loop. When one input is high, it forces the loop into the corresponding state. That said, I'm disappointed this artic…
Your image appears as black on black, you might want to re-upload it or edit the URL. I could only see it by dragging it against a non-black background.
Good point otherwise on the clearer schematic!