User:John R. Brews

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I am a Professor Emeritus of Electrical Engineering from The University of Arizona, where I taught device physics and circuit design for just under two decades. Previously, I was a research scientist for twenty-odd years at Bell Laboratories, Murray Hill, doing theoretical work in the areas of solid-state physics and device physics. I also am a Fellow of the IEEE, and a recipient of the Electron Device Society distinguished service award for work as Editor-in-chief of the journal IEEE Electron Device Letters, founded by Nobel prize winner George E. Smith. I've published a number of technical books and papers, some of which may be found at this link.

Images

Magnetism

(CC) Image: John R. Brews B-field lines near uniformly magnetized sphere     (CC) Image: John R. Brews Magnetic flux density vs. magnetic field in steel and iron

Widlar current source

(CC) Image: John R. Brews Widlar current source using bipolar transistors     (CC) Image: John R. Brews Small-signal circuit for finding output resistance of the Widlar source     (CC) Image: John R. Brews Design trade-off between output resistance and output current in Widlar source

Forces

(CC) Image: John R. Brews Force and its equivalent force and couple     (PD) Image: John R. Brews Centripetal force FC upon an object held in circular motion by a string of length R. The string is under tension FT, as shown separately to the left.     (PD) Image: John R. Brews Upper panel: Ball on a banked circular track moving with constant speed v; Lower panel: Forces on the ball.     (PD) Image: John R. Brews Polar unit vectors at two times t and t + dt for a particle with trajectory r ( t ); on the left the unit vectors uρ and uθ at the two times are moved so their tails all meet, and are shown to trace an arc of a unit radius circle.     (PD) Image: John R. Brews Local coordinate system for planar motion on a curve.     (PD) Image: John R. Brews Exploded view of rotating spheres in an inertial frame of reference showing the centripetal forces on the spheres provided by the tension in a rope tying them together.     (PD) Image: John R. Brews Rotating spheres subject to centrifugal (outward) force in a co-rotating frame in addition to the (inward) tension from the rope.     (PD) Image: John R. Brews The "whirling table". The rod is made to rotate about the axis and (from the bead's viewpoint) the centrifugal force acting on the sliding bead is balanced by the weight attached by a cord over two pulleys.     (PD) Image: John R. Brews Force diagram for an element of water surface in co-rotating frame.     (PD) Image: John R. Brews An object located at xA in inertial frame A is located at location xB in accelerating frame B.     (PD) Image: John R. Brews An orbiting but fixed orientation coordinate system B, shown at three different times.     (PD) Image: John R. Brews An orbiting coordinate system B in which unit vectors uj, j = 1, 2, 3 rotate to face the rotational axis.     Crossing a rotating carousel walking at constant speed, a spiral is traced out in the inertial frame, while a simple straight radial path is seen in the frame of the carousel.     (PD) Image: John R. Brews Rotating shaft unbalanced by two identical attached weights.     (PD) Image: John R. Brews An ellipsoid showing its axes     (PD) Image: John R. Brews While the pendulum P swings in a fixed plane about its hanger at H, the planes of the Earth observer rotate.     (PD) Image: John R. Brews As time progresses each unit vector's change is orthogonal to it.     (PD) Image: John R. Brews Tossed ball on carousel. At the center of the carousel, the path is a straight line for a stationary observer, and is an arc for a rotating observer.     (PD) Image: John R. Brews From the center of curvature of the path, the ball executes uniform circular motion.

Electromagnetism

(CC) Image: John R. Brews Electric motor using a current loop in a magnetic flux density, labeled B

Devices

(PD) Image: John R. Brews Cross section of MOS capacitor showing charge layers     (PD) Image: John R. Brews Three types of MOS capacitance vs. voltage curves. VTH = threshold, VFB = flatbands      (PD) Image: John R. Brews Small-signal equivalent circuit of the MOS capacitor in inversion with a single trap level     (PD) Image: John R. Brews A modern MOSFET     (PD) Image: John R. Brews A power MOSFET; source and body share a contact.     (CC) Image: John R. Brews Calculated density of states for crystalline silicon.     (CC) Image: John R. Brews Field effect: At a gate voltage above threshold a surface inversion layer of electrons forms at a semiconductor surface.     (PD) Image: John R. Brews Occupancy comparison between n-type, intrinsic and p-type semiconductors.     (PD) Image: John R. Brews Nonideal pn-diode current-voltage characteristics     (PD) Image: John R. Brews Band-bending diagram for pn-junction diode at zero applied voltage     (PD) Image: John R. Brews Band-bending for pn-diode in reverse bias     (PD) Image: John R. Brews Quasi-Fermi levels in reverse-biased pn-junction diode     (PD) Image: John R. Brews Band-bending diagram for pn-diode in forward bias     (PD) Image: John R. Brews Fermi occupancy function vs. energy departure from Fermi level in volts for three temperatures     (PD) Image: John R. Brews Fermi surface in k-space for a nearly filled band in the face-centered cubic lattice     (PD) Image: John R. Brews A constant energy surface in the silicon conduction band consists of six ellipsoids.     (PD) Image: John R. Brews Planar Schottky diode with n+-guard rings and tapered oxide.     (PD) Image: John R. Brews Comparison of Schottky and pn-diode current voltage curves.     (PD) Image: John R. Brews Schottky barrier formation on p-type semiconductor. Energies are in eV.     (PD) Image: John R. Brews Schottky diode under forward bias VF.     (PD) Image: John R. Brews Schottky diode under reverse bias VR.     (PD) Image: John R. Brews Critical electric field for breakdown versus bandgap energy in several materials.     (PD) Image: John R. Brews Schottky barrier height vs. metal electronegativity for some selected metals on n-type silicon.

Vestibular system

(PD) Image: John R. Brews When the semicircular canal stops rotating, inertia causes the cupula to register a false rotation in the opposite sense.     (PD) Image: John R. Brews Top: The semicircular canals with head erect. Bottom: the canals with head tipped forward.