TABLE OF CONTENTS Phil Perkins
| Note | Phil works on test circuits such as a V-I card, which can force a V or I into a test load and can also read the I or V on the load at the same time. I have worked on and designed this kind of V-I circuit, and it is a good challenge. Phil leads us to appreciate the problems in making such a tester "universal" and tolerant of every kind of load. Not easy, not impossible, but it does indicate the interaction among the circuit engineer, the customer, and the customer's system. How do you know what your customers need?/rap |
I like designing feedback loops. I have been designing and building feedback controlled systems for audio and low-frequency control since high school. My interest in high-fidelity audio started in the late 1950s. Transistors were scarce and not very good, so I worked with vacuum tube circuits. I learned that negative feedback would improve just about every characteristic of an audio amplifier. I built Heathkits and modified them to suit my own preferences. I experienced oscillation when there was too much feedback.
For a freshman project at MIT, I learned how negative feedback could transform an unstable device into a stable one. I built a device to suspend a steel ball a fraction of an inch below an electromagnet driven by a tube amplifier. The position of the ball was sensed by a light shining on a photocell. The ball would partially interrupt the light as...
