Fan-In/Fan-Out - Circuit - Explain why this circuit does not work

Problem: Explain why this circuit does not work for Fan-In=1 and Fan-Out=3 for all logic gates(including the complex logic gate).

Firstly, I would say the Inverter Gate is fine because it does not violate the Fan-Out=3. But I don't know what the problem is in the case of Fan-In=1.

Secondly, I would say that because x is routed to the 3 inputs of the complex logic that the Fan-In=3 thus it would overload the inverter thus making the gate not work properly.

Am I right? Hope somebody can give me a lead and or help me.

1 Answer

Figure 1. Fan-in count.

Does that help?

• Could it be that the complex logic gate can not handle 3 Inputs because the Fan-In=1? – M.Hisoka Nov 25 '17 at 21:29
• How many inputs is 'X' driving? – Transistor Nov 25 '17 at 21:47
• X drives 4 inputs. So I would say that I need to add extra gates to make the circuit work? – M.Hisoka Nov 25 '17 at 22:05
• Your question doesn't ask how to make it work. It asks why it doesn't. I've answered that. Yes, if the fan-in is too high you will need buffers. – Transistor Nov 25 '17 at 22:13