Graphic Credit

This web graphic was designed by Amrys Williams of MIT Web Communication Services, with circuit design by Riad Wahby and Scott Johnston.

The circuit is a simple linear series voltage regulator. AC voltage applied to the two terminals in the top left is rectified by the the four diodes in the "M". This voltage is applied to the capacitor, which stores the voltage and smoothes the ripples left by the diodes. Current through the resistor reverse-biases the zener diode, forcing the base of the transistor to a voltage set by the reverse-breakdown voltage of the zener diode. This voltage (minus the base-emitter drop) appears at the emitter of the transistor. Rigorous analysis reveals that the voltage at the emitter is dependent only on the voltage across the zener diode. Thus, as long as the zener diode remains reverse-biased, the regulator will put out a stable voltage.

The MIT home page is an interactive site with the goal of informing and engaging the MIT community and visitors. The Spotlight, with a changing graphic that calls attention to the new topic, supports MIT's mission and reflects the diversity of MIT itself. It does not represent a single voice but rather many voices, showing the Institute in a full and evolving way. The changing nature of the Spotlight reflects this goal of diversity by integrating and showcasing a multitude of aspects of MIT.