– Transistors and their connection to logic gates.

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– Transistors and their connection to logic gates.

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Anonymous 0 Comments

Logic gates are an abstraction. They represent the idea of taking binary inputs and giving binary outputs. Transistors are electronic components that are used to implement logic gates in physical hardware.

Imagine you have a pipe with two valves built in, and you need both valves open to let water through, you’ve got yourself a hydraulic AND gate. If you have the pipe split in two and rejoin again, with both sides of the split getting a valve, you’ve got a hydraulic OR gate.

To complete the analogy, say instead of turning the valves by hand you invent a valve controlled by water pressure. If you have both a valve that turns on when it’s actuated, as well as one that turns the water off when it’s actuated, that’s actually a pretty good analogy for how certain types of transistor work. Now you can feed the output of one gate into the input of the next, and you’re away building a hydraulic computer.

Anonymous 0 Comments

A logic gate is a theoretical construct that takes two (usually) binary inputs and outputs one binary output. So, for example, an AND gate outputs yes/TRUE/1/yay!/whatever when both inputs are yes/TRUE/1/yay!/whatever and no/FALSE/0/nope!/whatever otherwise.

You use logic gates to do binary arithmetic and logic operations, which are fundamental to modern computing.

*A* way to implement a logic gate in hardware is with an electric switch. In that case, the binary states are “high voltage” and “no voltage” or, less commonly, “current” and “no current”, or “open” and “closed” if you talk about the switch circuit itself. You can do this with any switch…a common household light switch, a relay, a vacuum tube, or…a transistor. A transistor, in the logic gate context, is just a very small, very fast, electronically controlled electric switch.

The first big jump in computing came when we went to electrically switched switches, rather than mechanically switched switches (from relays to vacuum tubes) because now there’s no moving parts and you can go a *lot* faster. Then we got another big jump with transistors because they can be manufactured from semiconductors and produced in incredibly small and integrated packages in one shot, rather than wiring up a bunch of individual components. This brought the cost per switch so low that “everybody” could carry a few billion transistors around in the their pocket for cheap.