Page 120 - The Art and Science of Analog Circuit Design

James M. Bryant

9. Analog Breadboarding

Introduction

While there is no doubt that computer analysis is one of the most valu-
able tools that the analog designer has acquired in the last decade or so,
there is equally no doubt that analog circuit models are not perfect and
must be verified with hardware. If the initial test circuit or "breadboard"
is not correctly constructed it may suffer from malfunctions which are
not the fault of the design but of the physical structure of the breadboard
itself. This chapter considers the art of successful breadboarding of high-
performance analog circuits.
The successful breadboarding of an analog circuit which has been
analyzed to death in its design phase has the reputation of being a black
art which can only be acquired by the highly talented at the price of infi-
nite study and the sacrifice of a virgin or two. Analog circuitry actually
obeys the very simple laws we learned in the nursery: Ohm's Law,
Kirchoff's Law, Lenz's Law and Faraday's Laws. The problem, however,
lies in Murphy's Law.
Murphy's Law is the subject of many engineering jokes, but in its sim-
plest form, "If Anything Can Go Wrong—It Will!", it states the simple
truth that physical laws do not cease to operate just because we have over-
looked or ignored them. If we adopt a systematic approach to breadboard

MURPHY'S LAW
Figure 9-1,

Whatever can go wrong, will go wrong.

Buttered toast, dropped on a sandy floor,
falls butter side down.

The basic principle behind Murphy's Law is that
all physical laws always apply -
when ignored or overlooked they do not stop working.

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