In digital circuits when: A signal is ‘active low’ means that signal will be performing its function when its logic level is 0. A signal is ‘active high’ means that signal will be performing its function when its logic level is 1.
What is mean by active low output?
This means the output is active low. That just means that when the output is active it has a logic low value, rather than a logic high. So, when the corresponding value is present on the inputs (1001 for example) the corresponding output (9) will be low and the rest will be high.
Why is active low used?
Active low signals are used in digital circuitry to reduce errors caused due to interference(noise). If we use active high signals interference caused due to noise is also considered as a signal, so we use active low signals to prevent errors.
How do you indicate an active low?
The name of an active-low signal is historically written with a bar above it to distinguish it from an active-high signal. For example, the name Q, read “Q bar” or “Q not”, represents an active-low signal. The conventions commonly used are: a bar above (Q)
