How to Read a Schematic

Posted on Feb 6, 2014

Electronic circuits are presented in schematic form. A schematic is really a map showing the path the current takes through the various componenets. Each component is represented by a symbol, usually with either a label or a value (or both). The arangement of the components on paper is chosen to make the function of the circuit clear, and usually

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only vaguely resembles the actual construction of the device. The current path is shown with lines, again drawn for maximum clarity, with little concern for the length or position of the real wires. The layout of a schematic is designed to show the function, usually with signal progressing from left to right. The actual layout of the circuit will be quite different. All points on a line are electrically identical. This includes all branches of a line. When we discuss the properties of circuits, we will assume the wires are perfect conductors, with no resistence or propagation delays of any kind. In fact, when we talk about real wire, we will make drawings the show ideal wire with components connected illustrating various effects. This symbol is ground. All ground points in the schematic are connected together. Furthermore, these points represent places in the circuit that are at 0 volts for reference in measurements. Often the ground includes the metal chasis of a device, but not always. Labels. Each component should have a label, and there is a standard set of names. For instance, a resistor is labeled R, and this circuit has 7 of them. Presumably there is a table somewhere that tells what the values are. There is only one capacitor; instead of calling it C1, I just listed its value. The gizmo at the left of figure 1 represents a phone jack. The label implies a guitar will be connected here. You have to understand that...

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