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Not operation
- The not operation
- Description: This operation take a single value and negates it.
- Expression: f(x) = x'
- Sometimes written $\lnot x$, x
- I will use either x' (our book) or x (Many other books, but harder to make in html)
- Truth Table
- Building truth tables.
- For a truth table, list all possible permutations of the input
- Then list the output values.
- If there are n variables, there will be $2^n$ output values.
- When building a truth table,
- Write the $n$ input variables across the top.
- Then count from 0 to $2^n$ in binary under these.
- For not there is a single variable, so there are $2^1 = 2$ rows or output values.
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- The symbol for a not gate
- A triangle with a circle on the end.
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- Talk about drawing this on tests.
Not is sometimes called in inverter
- And we invert the input or output of a gate/circuit.
- The input is inverted, (not notted)
Not from transistors.
- We can implement a not gate from two transistors.
- A positive voltage goes to the emitter of the PNP
- A the emitter of the NPN is hoked to the ground
- The two collectors are hooked together and form the output of the circuit
- The input value (x above) is hooked to both bases.
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- The digital file
Not with other gates
- Nots are frequently displayed as just a circle with other gates.
- This is an and gate
- This is an and gate with the first input inverted
- To do this in digital
- Right click on the gate.
- Click on the button associated with Inverted inputs:
- Select the inputs you wish to invert.