As you can see, during the positive half-cycle of the applied ac, the voltage across the diode is the full applied ac voltage, while the circuit current is zero. Note that this behavior is not dependent on frequency; an ideal diode simply conducts current in one direction only, regardless of frequency.
Consequently, is a diode the same as a battery?
A diode and a battery are two totally different things. A battery is a source of power. It has a positive terminal and a negative terminal. A diode is a specialized electronic component with two electrodes called the anode and the cathode.
Voltage connected to the diode in this direction is called forward bias. But if you reverse the voltage direction, applying the positive side to the cathode and the negative side to the anode, current doesn't flow.
The positive end of a diode is called the anode, and the negative end is called the cathode. Current can flow from the anode end to the cathode, but not the other direction. If you forget which way current flows through a diode, try to remember the mnemonic ACID: “anode current in diode” (also anode cathode is diode).
A rectifier is an electrical device composed of one or more diodes that converts alternating current (AC) to direct current (DC). A diode is like a one-way valve that allows an electrical current to flow in only one direction. This process is called rectification.
A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses.
When voltage is applied across a diode in such a way that the diode allows current, the diode is said to be forward-biased. When voltage is applied across a diode in such a way that the diode prohibits current, the diode is said to be reverse-biased.
A light-emitting diode (LED) is a special kind of diode that glows when electricity passes through it. Most LEDs are made from a semi-conducting material called gallium arsenide phosphide. LEDs can be bought in a range of colours. In common with all diodes, the LED will only allow current to pass in one direction.
A transistor is a miniature electronic component that can do two different jobs. It can work either as an amplifier or a switch: Transistors can also work as switches. A tiny electric current flowing through one part of a transistor can make a much bigger current flow through another part of it.
Without telling Shockley about the changes they were making to the investigation, Bardeen and Brattain worked on. On December 16, 1947, they built the point-contact transistor, made from strips of gold foil on a plastic triangle, pushed down into contact with a slab of germanium.
Bipolar Junction transistors, different FET transistors, are current-controlled devices. A small current entering in the base region of the transistor causes a much larger current flow from the emitter to the collector region. Bipolar junction transistors come in two major types, NPN and PNP.
Transistor Tree Diagram. The transistors classification can be understood by observing the above tree diagram. Transistors are basically classified into two types; they are Bipolar Junction Transistors (BJT) and Field Effect Transistors (FET). The BJTs are again classified into NPN and PNP transistors.
The three main BJT amplifier topologies are:
- Common emitter.
- Common base.
- Common collector.
Steps to identify the NPN type transistor:
- Keep the Multimeter in the Diode mode.
- Keep the positive probe to the center pin (Base) of the transistor.
- Touch the negative probe to the pin-1 (Emitter).
- Similarly touch the negative probe to the pin-3 (collector) with respect to the pin-2.
See the Insulated-gate field-effect transistor chapter for the depletion mode device. The MOSFET, like the FET, is a voltage controlled device. A voltage input to the gate controls the flow of current from source to drain.
The field-effect transistor (FET) is a transistor that uses an electric field to control the electrical behaviour of the device. FETs are also known as unipolar transistors since they involve single-carrier-type operation.
A MOSFET is known as a voltage controlled device because a voltage applied to the gate controls the flow of current between the source and drain. For a BJT the principal is the same. It is a current controlled device because the base current controls the current flow from the emitter to collector.
BJT transistor are current controlled devices but FET transistor are voltage controlled devices. BJT transistors are called current-controlled devices because the collector current is controlled by the base current, according to the ratio called Beta.
BJT (bipolar junction transistor) are widely used an amplifier, oscillator, switch etc. It is a current-driven device (MOSFET is voltage driven), the output current is equal to the input current times a factor which is called Gain. A basic BJT has three pins: the Base, Collector, and Emitter.
Therefore BJTs are more suitable than MOSFETs for driving low-power LEDs and similar devices from Micro Controllers Unit (e.g. Arduino). BJT can switch faster than MOSFET due to the less capacitance at the control pin. However MOSFET is more tolerant to heat (stable to thermal changes) and can simulate a good resistor.
The main difference between the NPN and PNP transistor is, an NPN transistor turns on when the current flows through the base of the transistor. In this type of transistor, the current flows from the collector (C) to the emitter (E). A PNP transistor turns ON, when there is no current at the base of the transistor.