34 lines
1.5 KiB
Markdown
34 lines
1.5 KiB
Markdown
---
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tags: [circuits]
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---
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# Digital circuits
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Ultimately every process in a computer is the product of a digital
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[circuit](Circuits.md) that is
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working on binary values. In contrast to electrical circuits, digital circuits
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are not represented in an
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[analogue](Analogue_and_digital.md) fashion.
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Analogue circuits work on the basis of real continuous phenomena in the world:
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charges and currents. As a result, the key properties of a circuit - voltage,
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current and resistance - can vary over a wide range of values. This is the
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reason that we require components like batteries and resistors: to control the
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natural flow of current and ensure that it only runs within desired parameters.
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In a standard electrical circuit, voltage, current and resistance can vary over
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a wide range of values however in the binary context we want to deal with
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discrete values (zeros and ones) which can be fed into the various
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[logic gates](Logic_gates.md).
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We therefore need a way to represent 'on' and 'off' as single quantities. We do
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this by stipulating that a given voltage corresponds to 'on' (high) and another
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corresponds to 'off' (low). Of course these are not really discrete values since
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voltage is inherently analogue but we basically binary-encode them. Formally
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'on' has a voltage of 1 and 'off' has a voltage of 0. In reality 'on' tends to
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be within 2-5V depending on the circuit design and anything between 0 - 0.8V is
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considered off.
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The [transistor](Transistors.md) is
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the electrical component that enables us to represent given voltage ranges as
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being 'on' or 'off'.
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