Pnp transistor tutorial the bipolar pnp transistor. The most commonly used transistor switch is the pnp variety shown in figure 1. Features and benefits 300 mw total power dissipation very small 1. Switch is a very useful and important application of transistors. This is a schematic diagram for a circuit that uses an npn. This is because when the current through the inductive load is suddenly broken when the transistor turns off, a back emf will build up as the magnetic field breaks down the voltage across the coil quickly increases or.
Switch controlling a relay switch controlling a dc motor flywheel diode a flywheel diode is often required with an inductive load. You can always remember that the arrow points at the n material. Below is the circuit for connecting a pnp transistor, which can function as a switch or an amplifier. How to use a transistor as a switch in different applications. If a lowinput signal is applied, then a highoutput signal is created. You can understand more clearly with the help of circuit digram of transistor used as a switch. The transistor in which one ntype material is doped with two ptype materials such type of transistor is known as pnp transistor. The bipolar junction transistor bjt as a switch bipolar. In cutoff region, the transistor operate as an open switch.
Bc558 silicon pnp transistor audio amplifier, switch features. And hence, transistor behaves like a close switch and start flowing current between collector and emitter. It is also a very useful circuit for an electronics hobbyist as it can be used as a driver, inverter etc circuit diagram. This type of switching is used for negative ground configurations. Applications highspeed, saturated switching applications for industrial service in thick and thinfilm circuits. And a normally open pushbutton is connected to the base of the transistor. To turn the pnp transistor operating as a switch on, the base terminal is connected to ground or zero volts low as shown. Switching and amplification are the two areas of applications of transistors and transistor as a switch is the basis for many digital circuits. Pnp transistor as a switch the circuit in the above figure shows the pnp transistor as a switch. Npn and pnp transistor switches cornerstone robotics. The main difference between pnp transistor and npn transistor is that the conduction in npn transistor is due to electron while conduction in pnp transistor is due to holes. I know this can sound a bit confusing, so read on to see how you can design a circuit with the pnp transistor. In pnp type transistor we need a negative voltage at the base terminal for turning on the. Pnp switching transistor bsr12 features low current max.
Npn transistors can be used to switch ground to a device. To understand how a pnp transistor works, simply flip the polarity or and npnpnp general purpose transistor 20 may 2019 product data sheet 1. Pnp transistor switching circuit the concept of pnp transistor as a switch is that, the current stops flow from collector to emitter only when a minimum voltage of 0. In an ideal switch, the transistor should be in only one of two states. Pnp transistor is the types of bipolar junction transistor. The problem is that the emitterbase junction is always forward biased. Dc operation of bipolar junction transistors bjts the bipolar junction transistor bjt is constructed with three doped semiconductor regions separated by two pn junctions regions are called emitter, base and collector. To understand how a pnp transistor works, simply flip the polarity or and a can connect a pnp transistor on the 12v high side, and connect the base to the collector of an npn. The symbol of the transistor has an arrow on the emitter.
This time however, the emitter is tied high, and the load is connected to the transistor on the ground side. Apr 24, 2019 pnp transistor as a switch the circuit in the above figure shows the pnp transistor as a switch. By relating these junctions to a diode model the pnp bjt may be modeled as shown on figure 2. In this article, the basic overview of transistors switching theory and the basic pnp and npn transistor working as switch, applications. In this case, i would make the following connections. General description npnpnp transistor pair in a sot666 plastic package. Experiment 6 transistors as amplifiers and switches our final topic of the term is an introduction to the transistor as a discrete circuit element. Pnp transistor as a switch pnp transistor works same as npn for a switching operation, but the current flows from the base. For this to happen we need to know the maximum load current for the device to be turned on and the minimum hfe of the transistor. High voltage fastswitching pnp power transistor features high voltage capability fast switching speed applications lighting switch mode power supply description this device is a high voltage fastswitching pnp power transistor. Pnp highside transistor switching with microcontroller. The equation of current in pnp transistor is given below. The functioning of both npn and pnp transistor is same but differ in terms of their biasing and power supply polarity. Generally, the pnp transistor can replace npn transistors in most electronic circuits, the only difference is the polarities of the voltages, and the directions of the current flow.
The first important thing to bear in mind to use a current limiting resistor at base. To explain with a pspice model, pn2907a transistor has been selected. Since an integrated circuit is constructed primarily from dozens to even millions of transistors formed from a single, thin silicon crystal, it. Pinning marking pin description 1 base 2 emitter 3 collector type. Mar 28, 2017 the above diagram show a typical microcontroller interface circuit using npn transistor. Alternatively, we can use a pnp transistor to create a highside switch. Difference between npn and pnp transistor with comparison. Mmbt3904 npn switching transistor in a sot23 plastic package. Pnp transistor circuit characteristics, working, applications. This condition of transistor is act as a fullyon and this is saturation region. The low side switch is very simple as shown in figure 1a. Jun 21, 2018 the base of the transistor is used to switch current through the collector and emitter. By setting the base voltage of a pnp transistor to 0. Transistor as a voltage amplifier our mission is to provide a free, worldclass education to anyone, anywhere.
If the circuit uses the bjt transistor as a switch, then the biasing of the transistor, either npn or pnp is arranged to operate the transistor at the both sides of the iv characteristics curves shown below. The lowvoltage logic just has to feed sufficient current into the npn transistor to turn it fully on. The operation of the pnp and npn transistors mainly utilizes holes and electrons. In the transistor, every three regions emitter, base, and emitter has a. Pnp transistor switch we can also use the pnp transistors as a switch, the difference this time is that the load is connected to ground 0v and the pnp transistor switches the power to it. However, since the emitter, base, and collector in the pnp transistor are made of materials that are different from those used in the. Transistor has three terminals emitter, base, and collector. In most digital ics transistors will work as a switch to make power consumption very low. A properly biased pnp transistor the pnp transistor works essentially the same as the npn transistor. That 1 npn transistor is, if a highinput signal is applied, a lowoutput sig 1 pnp transistor nal is created. A transistor can be operated in three modes, active region, saturation region and cutoff region. Basic construction of bipolar junction transistors. One fundamental circuit is the transistor switch, test leads in a commonemitter fashion inverts a signal.
The pnp transistor has two crystal diodes connected back to back. This means that most of the charge carriers in a pnp are holes. When the switch is turned off, the transistor base is grounded and the led is turned off. Using a transistor as a switch has some advantages. The pnp transistor is a type of bipolar transistor used for amplification and switching purpose and for the designing of the complementary output stage in combination with npn transistor. The two circuits in figure 12 illustrate the connections for an npn and a pnp sensors connections to a compatible controller and its internal. The transistor is a three semiconductor current controlled device. The choice between npn and pnp is really arbitrary. Similar to the npn circuit, the base is our input, and the emitter is tied to a constant voltage. If the transistor is a pnp, then the arrow points to the base of the transistor, otherwise it points to the output. The secret to making a transistor switch work properly is to get the transistor in a saturation state. Driver stages and low power output stages absolute maximum ratings. Pnp transistor works same as npn for a switching operation, but the current flows from the base.
Dec 19, 2016 by setting the base voltage of a pnp transistor to 0. Cutoff the transistor is fullyoff operating as a switch and. Since an integrated circuit is constructed primarily from dozens to even millions of transistors formed from a single, thin silicon crystal, it might be interesting and instructive to. Working of transistor as a switch npn and pnp transistors. The transistor is off when theres no bias voltage or when the bias voltage is less than 0. It is manufactured using high voltage multi epitaxial planar technology for high. The application of an pnp transistor is to work as a high side switch. Introduction to pnp transistor the engineering projects. These transistors can be used as amplifiers, switches and oscillators. The switch is on when the base is saturated so that collector current can flow without restriction. The operation of this circuit is very simple, if the input pin of transistor base is connected to ground i. The small amount of base current controlled both the emitter and collector current.
The transistors pnp and npn are bjts and it is a basic electrical component, used in various electrical and electronic circuits to build the projects. There is a temptation to think that we could do the same trick with an pnp transistor as shown in figure 1b. It should be clear that one of the diodes in a transistor is in the forward direction emittercollector while one of the diodes is in the reverse direction. It comes with three terminals called emitter, base, and collector where small current at the base terminal is used to control large current at other terminals. As shown above, a pnp transistors emitter and collector are formed via ptype doping. Mar 10, 2018 pnp transistor is the types of bipolar junction transistor. So, basically in this type of transistor two ptype positive materials dope a single ntype positive material and the pnp configuration is established, and it is referred to as a pnp transistor. Another crucial difference between npn and pnp transistor is the direction of flow of current, the current in npn transistor flows from collector to emitter, on the contrary, the current in pnp transistor flows from. The symbol for the pnp transistor is electronicslab14. Apr 20, 2018 the rest of this article will discuss pnp characteristics and applications.
Npn and pnp transistors are two complementary types of bipolar junction transistors bjts. Lets look at all four transistor modes individually. However, since the emitter, base, and collector in the pnp transistor are made of materials that are different from those used in the npn transistor, different current carriers flow in the pnp unit. The rest of this article will discuss pnp characteristics and applications. A pnp transistor could also have been chosen for the job.
In pnp transistor, pnp stands for positivenegativepositive configuration. In the npn transistor circuit, when the switch is pushed to the on position, the transistor base is biased correctly and current will flow through the collectoremitter junction. Pnp transistors can also be used as switching devices and an example of a pnp transistor switch is shown below. Description pnp switching transistor in a sot23 plastic package. The circuit is formed by connecting a voltage divider circuit with pnp transistor. For the pnp transistor, the base terminal is always negatively biased with respect to the emitter. Bc558 silicon pnp transistor audio amplifier, switch.
The three terminals of the bjt are called the base b, the collector c and the emitter e. C c bb ee n n p a npn transistor c c bb ee n p p b pnp transistor figure 1. As a memory tool, think about the pnp transistor as a direct switch connected to the positive voltage supply and the npn transistor as a direct switch connected to the negative ground voltage. Difference between npn and pnp transistor elprocus. Bc847bvn npnpnp general purpose transistor 20 may 2019 product data sheet 1. Collector to emitter voltage v ce is approximately equal to zero ideally. The base of the transistor is used to switch current through the collector and emitter. We can also use the pnp transistors as a switch, the difference this time is that the load is connected to ground 0v and the pnp transistor switches the power to it. In the transistor, every three regions emitter, base, and emitter has a different width in the transistor. The above diagram show a typical microcontroller interface circuit using npn transistor.
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