Dead bug style

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A method for prototyping high-speed circuits that helps to eliminate capacitive coupling. The method gets its name from the idea that upside down IC's look like dead bugs with their legs sticking up in the air.

When prototyping high-speed circuits, generally in the RF range (>1-2MHz), capacitive coupling between traces can lead to signal degradation. The dead-bug style helps to eliminate this by building the traces in the air to maximize the distance and minimize the parallel runs that various leads travel with one another. The dead-bug style also has the advantage of having a monolithic ground plane which helps to minimize circuit noise.

The generic dead-bug style begins with a single-sided copper-clad PCB. The IC's are glued upside-down to the surface of the copper cladding. The circuit is wired up in the air above the IC's with ground connections bent over and tacked down to the ground plane. Care must be taken with IC's that are in conductive packages (metal cans), that the metal portion is meant to be at ground potential, otherwise it must be isolated from the ground plane when gluing down.

Shown below is a picture of a 10MHz amplifier that I built using this style of construction. The PCB material used here was very thin and flexible and could even be cut with scissors. Two thin strips were cut off and glued down to carry the positive and negative 15V. RCA jacks were used to provide power because I had several laying around not earning their keep.

Dead bug.jpg

Also included here is board-less construction, the parts are just joined by the wiring, and more or less suspended in space.

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