A circuit is an electrical or electronic device that directs current through conductors to perform one or more desired functions. circuits are the basic building blocks of electronic devices and systems. Most electronic devices contain a combination of active (transistor) and passive (resistor) components. The behavior of these components under various operating conditions determines the overall performance of the device.
The simplest form of a circuit is a direct connection between two points, called a “short circuit”. If there is any resistance in the path between those two points, then current will flow through that resistance and some voltage will be dropped across it. This voltage drop will cause power to be dissipated in the form of heat, which can damage the components or even start a fire. To prevent this from happening, we use devices called “fuses” or “circuit breakers” which will open the circuit if too much current flows through it.
More complex circuits are made up of many interconnected components, such as transistors, diodes, capacitors, inductors, and resistors. The choice and combination of these components allows for a wide variety of different behaviors and functions. In order to understand how these circuits work, we need to first understand the behavior of each individual component.
Transistors are semiconductor devices that can be used to amplify signals or switch currents ON and OFF. They are made up of three terminals: the base, collector, and emitter. The base-collector junction is normally forward biased (meaning that current flows easily from the base to the collector), while the base-emitter junction is reverse biased (meaning that very little current flows from the base to the emitter). When a small signal is applied to the base terminal, it causes a much larger current to flow between the collector and emitter terminals. This amplifying effect can be used in audio amplifiers or other types of amplifier circuits. Transistors can also be used as switches by applying a large enough signal to their base terminals so that they turn ON fully and allow maximum collector-emitter current flow; this effectively shorts out any resistance in series with them. Diodes are another type of semiconductor device which only conducts electricity in one direction; they have two terminals called anode (+) and cathode (-). Diodes are typically used in rectifier circuits where AC voltages need to be converted into DC voltages; they can also be used as protection against voltage spikes by clamping them across sensitive circuitry so that only positive voltages appear on one side while negative voltages appear on other side
(the diode would then block any excessive positive voltage from reaching vulnerable parts). Capacitors store electrical energy in an electric field between two metal plates; they have two terminals called positive (+) and negative (-). The capacitor charges up when voltage is applied across its plates; once charged up, it can maintain its stored energy for some time even after power has been removed from it (this makes capacitors useful for storing data in memory chips). Inductors also store energy but do so using magnetic fields instead of electric fields; like capacitors they have two terminals called positive (+)