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How to Calculate Fan-Out

In the world of electronic circuits and computers, gates are the building blocks that allow these devices to work. Different gates have different characteristics. Some gates can invert input signals, others are designed to add, subtract, multiply and divide. When multiple gates are connected together, it is important that the gate providing the power to the other gates has the ability to supply the power needed. The term fan-out refers to the number of gates that can be safely powered by one gate.

Things You'll Need

Gate or circuit documentation (data sheet)
Calculator
Pencil or pen

Instructions

- 1
  Look at the data sheets for the integrated circuits that will be connected together. If IC #1 will be used to feed IC #2, then you need to look for the minimum output current for IC #1. You will also need to find the maximum input current for IC #2.
- 2
  Divide the minimum output current of IC #1 by the maximum input current of IC #2. The resulting value is the fan-out for that particular IC combination.
- 3
  Ignore any values after the decimal point. For example, if the fan-out calculation equals 3.3 or 3.8, the fan-out would be 3 in both cases. This helps keep the primary IC from overloading.

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