Richard Wolfson

Relativity and quantum physics touch the very basis of physical reality, altering commonsense notions of space and time, cause and effect. Both have reputations for complexity, but the basic ideas behind relativity and quantum physics are, in fact, simple and comprehensible by anyone. The essence of relativity in a single sentence: The laws of physics are the same for all observers in uniform motion. Relativity and quantum physics are the gateway...

Discover how transistors can be used to increase voltage, current, or power of an electronic signal while faithfully reproducing the signal's time variation. See how biasing and load-line analysis play key roles in amplifiers, and help prevent distortion. Learn to design a simple one-transistor audio amplifier that increases the voltage of audio-frequency signals.

Understand the math behind two basic rules that allow op-amps to leverage the magic of negative feedback: no current flows into op-amp inputs, and with negative feedback, V+ = V -. See how these rules allow op-amps to tame near-infinite gain in a circuit down to the exact amplification you want.

Examine the circuits that enable your devices to "remember" everything from contact information to your browsing history to the keystrokes you type on your computer. Compare random-access memory versus sequential memory as well as volatile and non-volatile memory.

Semiconductors make possible the transistors at the heart of electronics, including integrated circuits and computers. Learn how the atomic configuration of semiconductors makes them unique, and how engineers adjust their properties to make two types of semiconductors - P and N. Witness the critical role that PN-junctions play in semiconductor devices.

Now that the versatility of negative feedback has been demonstrated, adjust the strength of negative feedback in op-amp circuits to build amplifiers with whatever gain you choose. Create an amplifier that sums two or more inputs, see a circuit that converts current to voltage, and explore the design and operation of an op-amp-based light meter.

Observe how circuit designers have formulated a wide array of schemes for converting analog signals to digitally encoded information. See how flash converters, integrating converters, and feedback converters use very different methods to accomplish the same goal, and weigh the situational costs and benefits of each.

Flip-flops can be connected together to create counting circuits. Examine the circuitry behind 2-bit, n-bit, and decade counters, then see how the interruption of a light beam can be used in conjunction with such a circuit to keep count of people walking by or products moving along an assembly line.

Because we live in an analog world - sound, time, temperature, speed, and light are all analog phenomena - it's important to be able to convert outputs of digital circuits into analog signals that we can perceive. Discover two digital-to-analog converters (DACs): weighted-resistor DACs, and the delta-sigma DACs that provide high-resolution audio for our smartphones and mp3 players.

See how distinctly different electrical circuits can implement basic logic operations, and how simple logic gates come together to form complex logic circuits, ultimately including computers. Return to transistors to see how both BJTs and MOSFETs are used to implement logic gates, the latter in an arrangement called Complementary Metal Oxide Semiconductor (CMOS).