Wednesday, August 4, 2010

Ground plane circuit construction. What does this mean?

Q In QST I often see references to “ground plane” circuit construction. What does this mean?

A Ground-plane construction is a point-to-point technique that uses the leads of the components as tie points for electrical connections. You may also see it referred to as “dead bug” or “ugly” construction. (The term “ugly construction” was coined by Wes Hayward, W7ZOI.) “Dead-bug construction” gets its name from the appearance of an IC with its leads sticking up in the air. In most cases, this technique uses copper-clad circuit-board material as a foundation and ground plane on which to build a circuit using point-to-point wiring, hence “ground-plane construction.”

Ground-plane construction is quick and simple: You build
the circuit on an unetched piece of copper-clad circuit board.
Wherever a component connects to ground, you solder it to the copper board (see Figure 1). Ungrounded connections between components are made point-to-point. Once you learn how to build with a ground-plane board, you can grab a piece of circuit board and start building any time you see an interesting circuit.

A PC board has strict size limits; the components must fit in the space allotted. Ground-plane construction is more flexible; it allows you to use the parts on hand. The circuit can be changed easily—a big help when you are experimenting. The greatest virtue of ground-plane construction is that it is fast.

Circuit connections are made directly, minimizing component lead length. Short lead lengths and a low-impedance ground conductor help prevent circuit instability. There is usually less intercomponent capacitive coupling than would be found between PC-board traces, so it is often better than PCboard construction for RF, high-gain or sensitive circuits.

Figure 1—Typical ground plane construction. It may look ugly, but it is quick and easy.

From QST December 2000