Schematic diagrams define the components of the article that constitute a complete set and the interconnections between components; they usually give a detailed representation of the working principle of the article and may serve as a basis for developing other design documents, such as electrical installation blueprints and specification sheets.
The MOSFET is a versatile device, acting as a voltage-controlled current source in the saturation region and approximately as a voltage-controlled resistor in the resistive region. It can also be electronically controlled between cutoff and the resistive region to make it act as a switch, while for small signals around an operating point in the saturation region it acts as a linear amplifier. Another feature of the MOSFET is that, besides the categories of n-channel and p-channel devices, there are also enhancement- and depletion-mode devices of each category. In practice, for electronic circuit considerations, an n-channel device has Vth > 0 for enhancement-mode devices and Vth < 0 for depletion-mode devices, while the signs are reversed for p-channel devices.
Electric circuit theory is often divided into special topics, either on the basis of how the voltages and currents in the circuit vary with time (direct-current, alternating-current, nonsinu-soidal, digital, and transient circuit theory) or by the arrangement or configuration of the electric current paths (series circuits, parallel circuits, series-parallel circuits, networks, coupled circuits, open circuits, and short circuits). Circuit theory can also be divided into special topics according to the physical devices forming the circuit, or the application and use of the circuit (power, communication, electronic, solid-state, integrated, computer, and control circuits).
Circuit diagrams can be classified into four types: schematic diagrams, wiring diagrams, basic diagrams, and design diagrams. Schematic diagrams depict the functional components of an electric circuit and their interconnections. Wiring diagrams (for connections and junctions) show the arrangement of circuit components and of connecting wires.