1B: Comparing Macroscopic and Microscopic Circuit Components
||These are examples
of capacitors used in wired circuits. Capacitors are characterized
by their ability to store a charge and then release that charge
when it is needed. A capacitor in your car allows time-delayed
shutoff of interior lights after the door is shut. Televisions
use a capacitor to provide the current to display an image almost
as soon as the switch is turned on. Can you think of other everyday
places that capacitors might be used?
of layers of conducting (usually metallic) layers sandwiched
with insulating layers. In this example 2 layers each of thin
metal foil and insulating paper are stacked alternately. The
stack is then rolled (like a jelly roll) producing a cylinder
with the alternating layers. The number of insulating layers,
their inherent insulating ability, and the thickness of each
layer combine to determine the capacitance, or strength, for
semiconductor (MOS) capacitor from an integrated circuit shows
how the layer concept is applied to the microelectronic capacitor.
Can you predict which are the conducting and insulating layers?
To check your predictions, you should watch the movie "Making a Capacitor."
Approximately how thick is the insulating layer between the conductors?
||Resistors for macroscopic
circuits come in a wide variety of sizes. Resistors control the
amount of current in a circuit.
||Resistors are constructed
many different ways. The common theme is that current flow through
the circuit is retarded by a region with a lower ability to conduct.
In this illustration the current flowing through the wire is
reduced by a mixture of conducting and insulating solids.
||Current flows through
the p- region of this integrated circuit resistor. Resistance
arises from the smaller cross-section of the p-region
in the center. The current cannot cross over to the n-
region. The gray posts are metal contacts to connect to circuitry.
||A diode will only
allow current to flow in one direction. Diodes are used in applications
where one wants to control the polarity of current such as in
converting alternating current (AC) to direct current (DC). Light-emitting diodes
and photodiodes are used to transmit and receive light of specific
||This is a cartoon
cross-section of a diode like those pictured above. The colored
area marked n-has excess electrons; the colored
area marked p- has a deficiency of electrons. The
basis for a modern diode's unidirectional nature is the fact
that current flows much more efficiently from an n- region
to a p- region, and not the other way.
||In the diode components
of integrated circuits, the p- and n- regions are
retained. Since the entire component is embedded in n-type
Si, the n region of the diode is more heavily modified
(n+). The gray cylinders on the surface are metal contacts
which, in a complete circuit, would protrude through an insulating
layer to connect the diode to the rest of the circuit.
such as this one are common components of home electronics kits.
In this specialized kind of diode, light is emitted when the
electrical current flows.
will be individually wired to a circuit board, for example in
an old transistor radio. Internally, they are constructed very
similarly to microelectronic transistors. They just have pieces
large enough to be cut and assembled with machines.
||The metal-oxide semiconductor
(MOS) transistor used in integrated circuits revolutionized the
electronics industry. It is constructed of silicon, regions of
doped (modified) silicon, silicon dioxide, and metal conductors
which have sub-micrometer dimensions. Do you know the functions
of the different layers? Do you know how chemistry is used to
build this? Find out by viewing the movie "Making
Links to Integrated Circuit Processing Information
Comparing Macro and Micro Electronic Circuit Components | Computer Chip Thermochemistry | ChemConnections