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Schematic Diagrams and Symbols
Peter MathysECEN 1400
Circuits and Devices
• A circuit is a collection of interconnected electrical devices such that charge (usually electrons) can flow through it continuously without beginning or end.
• Each electrical device is a component that is treated as a separate entity.
• Devices typically encountered in circuits are batteries, resistors, capacitors, inductors, diodes, transistors, OpAmps, integrated circuits, etc.
Circuit Symbols
• To specify and document electrical circuits, standardized symbols are used for the devices and the wires that interconnect them.
• Circuit symbols are also used for conceptual devices such as ideal voltage and current sources, and to simplify schematics, e.g., by using a common reference or ground potential with an associated ground symbol.
Example
Physical CircuitCorresponding Schematic Diagram
(Ideal) Sources and Ground
In electronic circuits ground is used as an electrical reference point.
In electrical power distribution systems ground (“earth”) is the electrical potential of the Earth’s conductive surface.
Example Using Ground
Simple flashlight circuit with voltage source, switch, and lamp.
(a) All wires shown explicitly
(b) Bottom wire replaced by connection through ground.
(c) Using ground connections and battery as source.
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Switches
SPDT switch, construction view
Resistors
Color Code Standard Values
Standard values for resistors and other components. The most common values are shown in bold on the first line.
Diodes
Diodes are “one-way streets” for current.
Lamps and LEDs
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Capacitors Inductors, Transformers
Transistors (BJT)
BJT: Bipolar Junction Transistor
Transistors (JFET, MOSFET)
JFET: Junction Field-Effect Transistor
MOSFET: Metal Oxide Semiconductor Field-Effect Transistor
Operational Amplifiers Example
Switching Regulator: Simple but non-trivial example of a schematic.