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Buy Transistor 2021



Transistors are electronic semiconductor devices used to control or switch voltages and currents. The word transistor is derived from the word combination "transfer" and "resistor" and refers to the property of transistors to act as controllable resistors by changing the resistance of semiconductor layers. Nowadays, these semiconductor layers are mainly based on doped silicon.




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Generally speaking, the term transistor refers to bipolar transistors, often with the abbreviation BJT (bipolar junction transistor). They consist of three thin semiconductor layers that lie directly on top of each other. Each of these layers has an electrical connection that is led out of the enclosure. These connections are called base, emitter and collector (B, E, C). The semiconductor path emitter-collector forms the controllable current path, which is controlled via the base connection. The application of a relatively small base current influences the conductivity of the collector-emitter path, whereby the conductivity of the transistor without base current is close to zero and increases with increasing control current. This is physically comparable to a valve that requires very little actuation force, but can control large volumes. The factor between the base current and the collector emitter current is called the current gain. If the current amplification factor of a transistor is, for example, 100, a base current of 1 mA causes a current flow of 100 mA in the collector emitter path.


Basically, depending on the order of the three semiconductor layers, transistors are referred to as NPN or PNP transistors. The difference between these two types is visible in the circuit diagram by the small arrow at the connection of the emitter. With the NPN transistor, it points outwards, with the PNP transistor inwards. Similarly, NPN type transistors are suitable for positive voltages, with PNP transistors the polarities are reversed.


Darlington transistors interconnect two normal bipolar transistors to a pre- and main amplifier circuit in a single housing. This allows a much higher current gain to be achieved without the need for additional external wiring.


So-called "pre-tensioned transistors" integrate a bias resistor in their housing. This sets a defined base voltage to set the transistor operating point to the desired range, for example for audio and AC voltage applications.


Transistors are offered in a variety of housing designs, both in SMD technology and for conventional through-hole mounting (THT). Individual transistors for smaller power ratings are usually placed in a plastic housing. Power transistors generally have to be cooled; they therefore have a well heat-conductive metal casing or a metallic base plate for coupling to a heat sink or cooling surface.


Transistor arrays contain two to seven individual transistors. They are space-saving and simplify the handling. As with many other types of housing, suitable plug sockets are available from Conrad. A later required replacement can be carried out without soldering.


If high current amplification is required, Darlington transistors are well suited. In many cases, this means that a separate pre- and main reinforcement together with additional required components can be dispensed with. For example, transistors are available as matched pairs for audio applications and multi-channel amplifier circuits. These selected transistors have small differences between each other and ensure the best possible linearity in parallel operation. RF transistors are particularly suitable for higher frequencies due to their special properties.


Transistor arrays enable the development of more compact circuits than with the exclusive use of single transistors. Especially for smaller services, they represent an advantageous and space-saving solution, which also brings advantages in manufacturing during assembly and soldering.


The names NPN and PNP must not be confused with each other in all types and designs, as both transistor types are not interchangeable. The amplification factor of the transistor is an important characteristic, it should fit as closely as possible to the intended task, and the amplification bandwidth must also be sufficient. In order to operate a transistor within the safe working area, the required information is available in the respective data sheet.


In the case of new circuit developments, an exact attention should always be paid to the respective electrical values according to the data sheet, in order to select the transistor model that is best suited to the task. The load capacity of transistors does not extend to the limit, brings advantages in terms of reliability and long-term functional reliability. Use in more demanding ambient conditions requires compliance with the permissible temperature range and may require derating in a warm environment. In these cases, select a transistor with corresponding power reserves.


If a defective transistor has to be replaced, the same type should be used as far as possible. If this is no longer available, there are comparison tables with which an electrically compatible transistor can generally be found. The housing design also deserves attention: Is the pitch correct for wired types or the position and size of the solder pads for SMD transistors? Is the housing itself compatible with the available space and any existing heat sinks and mounting holes?


Ensure that any required test marks and compliance with the required standards are observed. The transistors offered in the Conrad shop are characterized by reliability and longevity and fulfill high quality requirements.


Like most electronic semiconductor devices, transistors are at risk from electrostatic discharge. Removal from the packaging and all subsequent handling and processing steps must therefore be carried out in accordance with the relevant ESD guidelines to avoid damage. It is also important to maintain the maximum permissible soldering temperature and the soldering duration to prevent overheating damage.


Depending on the type, a junction temperature of 150 to 200 C must not be exceeded for the silicon transistors used today. Higher temperatures either lead to immediate destruction or accelerate aging extremely. The permissible electrical values according to the data sheet usually refer to operation at 25 C ambient temperature. Higher ambient temperatures require derating; the corresponding diagrams can be found in the data sheet.


The most critical specs will be the current rating (collector current) and the power rating.* Almost any transistor can handle the low voltages (say 5V or 24V) that we are working with. The other specs (such as gain) don't vary that much from transistor-to-transistor so we usually don't worry too much about those other specs/characteristics (especially in digital circuits) . ...So in most cases, you'd "pick any-old transistor rated for 1 Amp or more", or something like that. ...But, it's tricky for a beginner because you don't know what specs you can ignore and what specs are important for a particular application.


The NPN [u]TIP120[/u] (and it's PNP compliment, the TIP125) is very popular. It's actually not a single transistor, but a Darlington pair in one package (with a couple of other components). A Darlington behaves pretty-much like a regular transistor with higher beta (higher current gain), and about twice the base-emitter voltage.


...I've been playing around with electronics for many years, and I can't remember the last time I used a transistor on a home project! I've got a few boxes of spare parts... I keep a good selection of resistors, capacitors, voltage regulators, LEDs, 1N4007 diodes, op-amps, and maybe a few other things I like to keep "in stock".


Then, I've got lots of "random" ICs and connectors and things from previous projects (because I almost always buy extra parts) and I've probably got a few transistors somewhere, but it's not something I intentionally keep on-hand.


ONLY buy a mixed bag of transistors and read up on taking measurements from them with a multimeter. carry this out for a number of them from the mixed lot and bag them up, writing on the bag the values you get from the multimeter readout. make sure you have it sitting in the right slots for that type of transisistor.


BC548 is a bi-polar general purpose NPN transistor that is commonly used in switching and amplifying applications. It can found in relay driver, LED driver and other medium power switching devices and audio or signal amplifiers. The features of the BC548 transistor are:


A transistor is a semiconductor device that is used to amplify or switch electronic signals and power. It is made up of three layers of semiconductor material, each of which may carry a current. The base, collector, and emitter are its three terminals.


A transistor is a semiconductor device used to amplify or switch electronic signals and electrical power. It is composed of semiconductor material usually with at least three terminals for connection to an external circuit. Transistors are basically classified into two types; they are Bipolar Junction Transistors (BJT) and Field Effect Transistors (FET)


Transistors are three terminal devices, namely collector, emitter and base. When the minimum voltage of 0.7 (for Si) is applied between the base and the emitter, the channel between the collector and emitter opens, thus opening the circuit. In this mode the transistor acts as a switch. Similarly, the transistor can also behave in amplifying mode as the base-emitted voltage can be anywhere between fully on and fully off, thereby limiting the collector emitter channel.


MOSFETs are among the most popular types of transistors thanks to their versatility and widespread use. In this guide, we will explain how these transistors work as well as sharing practical tips for using MOSFETs and choosing the most suitable type of MOSFET. 041b061a72


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