Page 61 - Analog Circuit Design Art, Science, and Personalities

Reflections of a Dinosaur

rewarding. Your interface with the customer is usually over the phone, so you have
to develop a technique for trouble shooting at a distance. The person on the other
end of the phone line usually performs the measurements you request and verbally
communicates the results. In these situations take nothing for granted. What is
obvious to you is probably not obvious to the person on the other end of the line, or
you would not be on the phone in the first place. All the questions should be asked,
no matter how mundane they may bc. "Did you by-pass the power supplies with
both ceramic and tantalum capacitors to ground'!" Answers to such questions as this
will give you a better feel for the level of expertise at the other end of the line.
Customer interface can be rewarding, as you can sometimes solve a problem that
the customer has struggled with for somc time. Occasionally a situation will arise
that can make you a legend in your own time.
Several years ago T was testing a 12-bit DAC in the lab and obtaining some very
strange results. After performing the usual checks 1 round the -15 V supply had
become disconnected. The loss of the negative supply voltage resulted in the strange
behmior of the DAC. 1,reconnected the siipply and the unit worked fine. The next
day 1 was sitting in our application engineer's office when he received a call from a
customer who was having a problem. The customcr was tcsting the same model
DAC that had given me the strange problem the previous day. As luck would have
it, the problem he described was exactly the strange behavior I had witnessed the
day before. 1 played a hunch and told our application engineer to have the customer
check for a cold solder joint on the -15 V supply. The application engineer, looking
a little skeptical, conveyed the information. About 15 minutes Iatcr the customer
called back, verifying that his technician did find a bad connection on the -15 V
supply. He fixed the cold solder joint and the unit worked tine. I never told our
application engineer the whole story. Situations like that happen very seldom. so
when they do, milk them for all they are worth. That is how lcgends are born.
Even though digital technology has becoinc the glamor segment of the electronics
industrj,. analog design still provides excitement and challcnge for those of us who
enjoy the color gray. Integrated circuit technology has allowed the development of
complex analog circuits on a single silicon die. It is ironic that digital technology
has played a major role in making the new innovations in analog design possible.
Without simulators for design, CAD systems for layout, and digital measurement
systems for testing, analog tcchnology could not have advanced to its present state.
The design process has been highly automated, but a creative and innovative mind
is still a requirement for good circuit design. It was once said that, "Anyone who
can be replaced by a computer should be." The number of analog designers is
fewer, but until the world is quantized into "ones" and "zeros:" the analog circuit
designer still has a place in the electronic industry.
1 will close with an old story I first heard from Don Bruck, one of the founders
of Hybrid Systems. The story defines the difference between an analog and a digital
engineer. In keeping with contemporary demands. the story can be made less gender
specific by switching the male and female roles.

Two male engineers, one specialiing in digital design and the other in analog. are
working together in the laboratory. A nude female appears at the door, attracting the
attention of both men. The vision of beauty announces that every 10 seconds she will
reduce the distance between herself and the engineers by one hall: The digital engi-
neer looks disappointed and states, "That's terrible. she will never get here.'' The
analog engineer smiles and then replies, '.That's okay. \he will get close enough."
That is the essence of analog design-all else is explanation.

42