From Citizendium, the Citizens' Compendium
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Photos
Photos


(PD) Photo: John R. Brews

Mourning dove on nest in Tucson


(PD) Photo: John R. Brews

Morning dove with squab, Tucson AZ.


(PD) Photo: John R. Brews

Mourning dove with squab.


(PD) Photo: John R. Brews

Mourning dove squab.


(PD) Image: John R. Brews

Mourning dove on saguaro cactus, Tucson AZ.


Magnetism
Magnetism


(CC) Image: John R. Brews

Bfield lines near uniformly magnetized sphere


(CC) Image: John R. Brews

Magnetic flux density vs. magnetic field in steel and iron


(PD) Image: John R. Brews

Bfield from current I_{2} in wire 2 causes force F on wire 1.


Chemistry
Chemistry


(PD) Image: John R. Brews

Reactants cross an energy barrier, enter an intermediate state and finally emerge in a lower energy configuration.


Circuits
Current sources


(CC) Image: John R. Brews

Widlar current source using bipolar transistors


(CC) Image: John R. Brews

Smallsignal circuit for finding output resistance of the Widlar source


(CC) Image: John R. Brews

Design tradeoff between output resistance and output current in Widlar source


(PD) Image: John R. Brews

A current mirror implemented with npn bipolar transistors using a resistor to set the reference current I_{REF}; V_{CC} = supply voltage.


(PD) Image: John R. Brews

An nchannel MOSFET current mirror with a resistor to set the reference current


(PD) Image: John R. Brews

Gainboosted current mirror with op amp feedback to increase output resistance.


(PD) Image: John R. Brews

MOSFET version of wideswing current mirror; M_{1} and M_{2} are in active mode


(PD) Image: John R. Brews

Operationalamplifier based current sink. Because the op amp is modeled as a nullor, op amp input variables are zero regardless of the values for its output variables.


(PD) Image: John R. Brews

A digital inverter circuit using a bipolar transistor.


(PD) Image: John R. Brews

Transfer characteristic of bipolar inverter showing modes.



Collector current vs. input voltage for a bipolar inverter with V_{CC}=5V and R_{C}=1kΩ.


(PD) Image: John R. Brews

Input and output signals for bipolar inverter used as an amplifier.


(PD) Image: John R. Brews

Twoport network with symbol definitions.


(PD) Image: John R. Brews

Zequivalent two port showing independent variables I_{1} and I_{2}.


(PD) Image: John R. Brews

Yequivalent two port showing independent variables


(PD) Image: John R. Brews

Hequivalent twoport showing independent variables


(PD) Image: John R. Brews

Gequivalent twoport showing independent variables


(PD) Image: John R. Brews

Block diagram for asymptotic gain model


(PD) Image: John R. Brews

Possible signalflow graph for the asymptotic gain model


(PD) Image: John R. Brews

MOSFET transresistance feedback amplifier.


(PD) Image: John R. Brews

Collectortobase biased bipolar amplifier.


(PD) Image: John R. Brews

Twotransistor feedback amplifier; any source impedance R_{S} is lumped in with the base resistor R_{B}.


Smallsignal circuits


(PD) Image: John R. Brews

Smallsignal circuit for pndiode driven by a current signal represented as a Norton source.


(PD) Image: John R. Brews

Bipolar current mirror with emitter resistors


(PD) Image: John R. Brews

Smallsignal circuit for bipolar current mirror


(PD) Image: John R. Brews

Common base circuit with active load and current drive.


(PD) Image: John R. Brews

Commonbase amplifier with AC current source I_{1} as signal input


(PD) Image: John R. Brews

Bipolar transistor with base grounded and signal applied to emitter.


(PD) Image: John R. Brews

Commonbase amplifier with AC voltage source V_{1} as signal input


(PD) Image: John R. Brews

The result of applying Norton's theorem.


(PD) Image: John R. Brews

Bipolar current buffer.


(PD) Image: John R. Brews

Smallsignal circuit to find output current.


(PD) Image: John R. Brews

Smallsignal circuit with test current i_{X} to find Norton resistance.


(PD) Image: John R. Brews

The result of applying Thévenin's theorem.


(PD) Image: John R. Brews

Bipolar buffer.


(PD) Image: John R, Brews

Smallsignal circuit for voltage follower.


(PD) Image: John R. Brews

Determination of the smallsignal output resistance.


(PD) Image: John R. Brews

Simplified, lowfrequency hybridpi BJT model.


(PD) Image: John R. Brews

Bipolar hybridpi model with parasitic capacitances.


(PD) Image: John R. Brews

Simplified, lowfrequency hybridpi BJT model.


(PD) Image: John R. Brews

Bipolar hybridpi model with parasitic capacitances.


(PD) Image: John R. Brews

Simplified, threeterminal MOSFET hybridpi model.


(PD) Image: John R. Brews

Fourterminal smallsignal MOSFET circuit.


(PD) Image: John R. Brews

Miller effect: These two circuits are equivalent.


(PD) Image: John R. Brews

Smallsignal circuit for transresistance amplifier


(PD) Image: John R. Brews

Smallsignal circuit with return path broken and test current i_{t} driving amplifier at the break.


(PD) Image: John R. Brews

Three smallsignal schematics used to discuss the asymptotic gain model


Return ratio


(PD) Image: John R. Brews

Left  smallsignal circuit corresponding to bipolar amplifier; Center  inserting independent source and marking leads to be cut; Right  cutting the dependent source free and shortcircuiting broken leads.


Amplifiers


(PD) Image: John R. Brews

Some terms used to describe step response in time domain.


(PD) Image: John R. Brews

Ideal negative feedback model; open loop gain is A_{OL} and feedback factor is β.


(PD) Image: John R. Brews

Conjugate pole locations for step response of twopole feedback amplifier.


(PD) Image: John R. Brews

Stepresponse of a linear twopole feedback amplifier.


(PD) Image: John R. Brews

Step response for three values of time constant ratio.


(PD) Image: John R. Brews

Bode gain plot to find phase margin of twopole amplifier.


(PD) Image: John R. Brews



(PD) Image: John R. Brews



(PD) Image: John R. Brews

Bode magnitude plot for zero and for lowpass pole


(PD) Image: John R. Brews

Bode phase plot for zero and for lowpass pole


(PD) Image: John R. Brews

Bode magnitude plot for polezero combination; the location of the zero is ten times higher than in above figures


(PD) Image: John R. Brews

Bode phase plot for polezero combination; the location of the zero is ten times higher than in above figures


(PD) Image: John R. Brews

Gain of feedback amplifier A_{FB} in dB and corresponding openloop amplifier A_{OL}.


(PD) Image: John R. Brews

Phase of feedback amplifier °A_{FB} in degrees and corresponding openloop amplifier °A_{OL}.


(PD) Image: John R. Brews

Gain of feedback amplifier A_{FB} in dB and corresponding openloop amplifier A_{OL}.


(PD) Image: John R. Brews

Phase of feedback amplifier A_{FB} in degrees and corresponding openloop amplifier A_{OL}.


(PD) Image: John R. Brews

Operational amplifier with compensation capacitor C_{C} between input and output to cause pole splitting.


(PD) Image: John R. Brews

Operational amplifier with compensation capacitor transformed using Miller's theorem to replace the compensation capacitor with a Miller capacitor at the input and a frequencydependent current source at the output.


(PD) Image: John R. Brews

Idealized Bode plot for a two pole amplifier design.


(PD) Image: John R. Brews

Miller capacitance at low frequencies C_{M} (top) and compensation capacitor C_{C} (bottom) as a function of gain


Logic
Logic and Venn diagrams


(PD) Image: John R. Brews

Venn diagrams; set A is the interior of the blue circle (left), set B is the interior of the red circle (right).


(PD) Image: John R. Brews

Venn diagrams; set X is the interior of the blue circle (left), set Y is the interior of the red circle (right).


(PD) Image: John R. Brews

Venn diagram showing subsets of two sets X and Y.


(PD) Image: John R. Brews

Venn diagram for three sets X, Y, and Z.


(PD) Image: John R. Brews

Venn diagram for four sets X, Y, Z, and W.


(PD) Image: John R. Brews

Venn diagram for five sets X, Y, Z, V and W.


(PD) Image: John R. Brews

A threeinput logic gate (center) with its Venn diagram (top) and truth table (bottom).


(PD) Image: John R. Brews

Fiveswitch network with Venn diagrams for branches


(PD) Image: John R. Brews

Equivalent threeswitch network with Venn diagrams for branches


Forces
Forces


(CC) Image: John R. Brews

Force and its equivalent force and couple


(PD) Image: John R. Brews

Centripetal force F_{C} upon an object held in circular motion by a string of length R. The string is under tension F_{T}, 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 u_{ρ} and u_{θ} 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 corotating 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 corotating frame.


(PD) Image: John R. Brews

An object located at x_{A} in inertial frame A is located at location x_{B} 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 u_{j}, 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.
Image


(PD) Image: John R. Brews

Torque vector T representing a force couple.


(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 approximate circular motion.


(PD) Image: John R. Brews

Some useful notation for the ball toss on a carousel.


(PD) Image: John R. Brews

The ball follows a nearly circular path about the center of curvature.


(PD) Image: John R. Brews

The inertial forces on the ball combine to provide the resultant centripetal force required by Newton's laws for circular motion.


(PD) Image: John R. Brews

Stats for a particular path of ball toss.


(PD) Image: John R. Brews

Tangentplane coordinate system on rotating Earth at latitude φ.


(PD) Image: John R. Brews

Wind motion in direction of pressure gradient is deflected by the Coriolis force.


(PD) Image: John R. Brews

In the northern hemisphere, Coriolis force forms a counterclockwise flow.


(PD) Image: John R. Brews

Path of ball for four rates of rotation. Catcher positioned so the catch is made at 12 o'clock in all cases.


(PD) Image: John R. Brews

A fluid forced through a rocking tube experiences a Coriolis acceleration.


Electromagnetism
Electromagnetism


(CC) Image: John R. Brews



(PD) Image: John R. Brews

The Fizeau apparatus for measuring the speed of light by passing it between the cogs of a rotating gear and reflecting it back through adjacent cogs.


(PD) Image: John R. Brews

Measuring a length using interference fringes.


(PD) Image: John R. Brews

The wavelengths of standing waves in a box that have zero amplitude (nodes) at the walls.


(PD) Image: John R. Brews



(PD) Image: John R. Brews

Boat opposing incoming waves experiences the Doppler effect


(PD) Image: John R. Brews

Doppler shift with moving source


(PD) Image: John R. Brews

Infinitesimal current elements in two closed currentcarrying loops


(PD) Image: John R. Brews

Origin at 0, observation point at P, and present position of charge q distant by R from observation point P.


Devices
Devices


(PD) Image: John R. Brews

Mesa diode structure (top) and planar diode structure with guardring (bottom).


(PD) Image: John R. Brews



(PD) Image: John R. Brews

Gummel plot and current gain for a GaAs/AlGaAs heterostructure bipolar transistor.


(PD) Image: John R. Brews

QuasiFermi levels and carrier densities in forward biased pndiode.


(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. V_{TH} = threshold, V_{FB} = flatbands


(PD) Image: John R. Brews

Smallsignal 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.


(PD) Image: John R. Brews

Two bipolar transistor modes, showing extrapolation of asymptotes to the Early voltage.


(PD) Image: John R. Brews

Channel length modulation in 3/4μm technology.


(PD) Image: John R. Brews

Early voltage for MOSFETs from a 0.18μm process as a function of channel strength.


(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 ntype, intrinsic and ptype semiconductors.


(PD) Image: John R. Brews

Nonideal pndiode currentvoltage characteristics


(PD) Image: John R. Brews

Bandbending diagram for pnjunction diode at zero applied voltage


(PD) Image: John R. Brews

Bandbending for pndiode in reverse bias


(PD) Image: John R. Brews

QuasiFermi levels in reversebiased pnjunction diode


(PD) Image: John R. Brews

Bandbending diagram for pndiode 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 kspace for a nearly filled band in the facecentered cubic lattice


More Devices
Devices


(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 pndiode current voltage curves.


(PD) Image: John R. Brews

Schottky barrier formation on ptype semiconductor. Energies are in eV.


(PD) Image: John R. Brews

Schottky diode under forward bias V_{F}.


(PD) Image: John R. Brews

Schottky diode under reverse bias V_{R}.


(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 ntype silicon.


(PD) Image: John R. Brews

Theoretical dependence of Schottky barrier heights for diodes using pSiC vs. electronegativity of the metal according to Mönch


Vestibular system
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.

