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Design & Technology

Logic and microcontrollers

Using logic gates in electronic circuits

In electronic circuits, the logic gates are normally packaged as an integrated circuit. For example, the 4081 IC contains four AND gates.

Pinouts for 4018 IC

Pinouts for 4018 IC

Pull-down and pull-up resistors

When using digital integrated circuits (ICs), the input signal can sometimes vary slightly from the expected low value. One reason for this is that air can charge objects with static electricity, especially on hot dry days. This unwanted charge can cause the input pins to float high and make the IC 'think' incorrectly that an input is on.

Complex circuit with a 4081 chip and pull-down resistors

AND gate with two 10K pull-down resistors

In a similar way, pull-up resistors can be used to attach the input to the high-voltage rail if the input is expected to be high.

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