Page 42 - Analog Circuit Design Art, Science, and Personalities

Bernard Gordon

5. On Being the Machine
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The art of analog design per se is not generally very different from that of other
engineering endeavors. It is the purpose of this chapter to convey a visceral sense of
the art of engineering, particularly as related to creative or innovative conceptions.
Assume the engineer possesses, as a necessary minimum requisite for being an
analog designer, a broad and general knowledge of electronic circuit physics and
mathematics, the characteristics of available componentry, and the capabilities of
modern manufacturing processes. Furthermore, to produce competent designs capa-
ble of being manufactured in quantity and of retaining their desired performance
specifications, the engineer must have developed a thorough understanding, sensi-
tivity to, and appreciation of tolerances and error budgeting.
There remains, however, an additional criterion for being truly creative and not
merely competent. . . the development of sufficient art and skills to synthesize
innovative, inventive new devices (machines). What is needed is the ability to envi-
sion the purpose and totality of the device as a whole, in order to be able to syner-
gistically relate the parts of the design, minimize the number of elements, and
produce what must be described as an elegantly simple solution.
The creative designer must be able to develop the mindset of “being the machine,”
in order to become the “mental and living embodiment” of the circuit or system. The
ability to do so is less dependent on textbook learning and analysis than on devel-
oping the capacity, by experiencing a succession of increasingly complex problems,
to simultaneously conceive, pursue, examine, and compare multiple possible solu-
tions. The designer must then be able to envision the interrelationships, tolerances,
and weaknesses of components and processes and then consciously and suhcon-
sciously recognize what suddenly appears as a realization and visualization of an
elegantly simple coherent solution of interacting, self-supporting componentry.
As ii first simple example, consider the design of the acoustic memory that was
incorporated into the first commercial digital computer, Univac I, circa 1949. While
it was part of a digital computer and was employed for the storage of serial digital
words, the design requirements were basically analog in nature. The recirculating
loop. shown in Figure 5- I, was to consist of an input gate structure whose output
was applied to an RF modulator circuit, which in turn drove a piezoelectric trans-
ducer. which converted the electrical signal into mechanical vibrations. These vibra-
tions propagated acoustically through the mercury channel and impinged upon an
identical piezoelectric transducer, reciprocally producing the RF signal at highly
attenuated levels. This attenuated signal was to be amplified and demodulated and
returned to the gating structure for reclocking to pass through the loop again.
Univac I operated at a clock frequency of2.25 MHz, or approximately 0.444 msec
pcr pulse. The system design called for a rise time of approximately 0.2 msec, cor-

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