As communication circuits get faster and faster such as with USB 2.0, 10-Gigabit Ethernet, Firewire, and HyperTransport, analog principles become increasingly important. MOSFET device sizes get smaller to make the higher speeds possible. Consequently, trace and device parasitics become increasingly important. As frequencies get higher, the designer must be more aware of the effects of analog principles in the circuit. This paper addresses some of these issues including the use of current mode signals, when to use transmission line analysis, and some ways proper layout can reduce parasitics. Design examples of USB 2.0 transceivers will be used to illustrate these ideas.

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