Category: Bjt transistor characteristic curves

It is consist of two pn junctions. One junction is forward-biased, and the other is reverse-biased. B layer is usually thin, but characterised with high resistivity, so majority of careers will flow through into the C layer due to different doping levels of these materials. The main feature of BJT — small base-collector current controlling large collector current.

Bipolar junction transistor(BJT):Applications & characteristics

This configuration is called common-emitter as emitter is common for input and outp ut voltages. Here collector-base junction is reverse biased, and base-emitter junction is forward-biased. Input data will be here base-emitter, and output — collector-emitter.

In the active region here base-collector pn-junction is reverse-biased and base-emitter pn-junction is forward-biased. This configuration is called that, because base is connected to both — emitter and collector. The output characteristics of BJT can be divided into three areas — cut-off, saturation and active region.

In the active regionbase-collector pn-junction is reverse-biased, and base-emitter — forward-biased. In standard operation the BJT transistor works as an amplifier.

Important point to consider is self-biased BJT circuit, that is depicted below. It can be transformed into circuits that are much easier to consider from the point of view of BJT operation point. Using Thenevin theorem we can transform the circuit into the following circuit below with equivalent resistance and voltage source. The BJT becomes a switch as soon as the base is sourced by the AC signal, so it will work in the conducting regime to the blocking regime. The dynamic switching characteristics here are also very important, because the high-frequency velocity makes a huge impact on the losses of the device.

On figure below we can see the volt-ampere characteristics for the npn BJT. To drive it as an amplifier the transistor must be kept in its linear region.

bjt transistor characteristic curves

For using the transistor as a switch, it should operate from the cut-off region to the saturation region — turning on and turning off. The turn-on region is characterised by the increase in the collector current, when the collector-emitter voltage remains small. The depletion region in the transistor becomes very small and as conductivity increases, it corresponds to the saturation region in Figure 1.

The turn-off region is characterised with a high collector-emitter voltage and low collector current level, which corresponds to the cut-off region. So switching losses occur when the device switches in high frequency. The rising and falling times of the signal plays very important role. Tags: dynamic characteristics Post navigation Previous Post Magnetic induction vector circulation Next Post What is rotating electric machine You may also like Leave a Reply Cancel reply You must be logged in to post a comment.

Charges flow at the BJT are depicted on the figure below. Common-emitter configuration This configuration is called common-emitter as emitter is common for input and outp ut voltages. Common — base configuration This configuration is called that, because base is connected to both — emitter and collector. Previous Post.

Next Post. You may also like.Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It only takes a minute to sign up. I was going to make a voltage amplifier for weak signals with 2SD, but I noticed that the manufacturers haven't included the characteristic curves in the datasheets. How can I optimize the circuit if I don't know this transistor well?

Should I try to generate the curves myself before using this transistor? However you don't have the characteristic curves. That's the reality of semiconductor manufacturing. Some parameters are really difficult to control tightly. Therefore, you design your circuits so that the overall circuit characteristics do not strongly depend on the actual characteristics of any particular device. Then, when you are done, you go back and verify that the circuit operation is acceptable over the full range of possible characteristics for each device.

It sounds complicated, but you'll soon learn how to subdivide the problem to keep things under control. You apply the same concept to multi-stage circuits — you design each stage so that its performance does not depend strongly on what is connected to its inputs and outputs.

For example, in an amplifier, you use negative feedback to set the gain of the circuit so that it is not a strong function of the actual current transfer ratio of the transistor. This could be as simple as putting a resistor in series with the emitter. These transistors are 'binned' so you know the hFE over a fairly narrow range. So a good starting point would be 10mA Ic and design a bias arrangement to maintain the desired Vce.

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I have no idea who "New Jersey Semiconductor" is, but those parts were originally made by Rohm of Japan now discontinued. I still have a small cache of them.

Maybe they specialize in parts that are no longer available and people will pay big bucks for. Sign up to join this community. The best answers are voted up and rise to the top. How important are BJT characteristic curves when designing amplifiers? Ask Question. Asked 2 years, 4 months ago. Active 2 years, 4 months ago. Viewed 1k times. Improve this question. The actual target circuit defines how the transistor is used and whether the hFE limitations as seen in all BJTs might unduly affect desired performance.

In other words, with a proper design, the transistor limitations are largely eradicated; with a poor design you have side-effects due to transistor limitations. Data sheet suggests that low voltage noise requires a DC bias 10mA collector current.

You can expect a fairly low amplifier input impedance biased this way. Also - be aware that many bipolar transistors meant for higher-power applications don't spec noise at all - and are at least as good as this one. If I know the transistor well, I can choose the right values for the resistors.

More mutually exclusive requirements: most possible voltage gain and high temperature stability and drift. Show your circuit and take note of what will likely be said. Active Oldest Votes.

bjt transistor characteristic curves

Improve this answer. Dave Tweed Dave Tweed k 11 11 gold badges silver badges bronze badges. Spehro Pefhany Spehro Pefhany k 11 11 gold badges silver badges bronze badges.Hello dear students, I hope you all are doing great. The transistor was created in by J. Barden, W Shockley and W.

Bratterin in A transistor name was given to this component by John R.

Introduction to BJT (Bipolar Junction Transistor)

At the time of creation, it is known as a solid-state type of vacuum triode but knows known as a transistor.

It is an electronic component mainly used for amplification and switching purposes.

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As the name suggests, it is composed of two junctions called emitter-base junction and collector-base junction. If you have any question ask in comments, thanks for reading. I am a professional engineer and graduate from a reputed engineering university also have experience of working as an engineer in different famous industries.

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Related Posts. Bridged-T Attenuator Configuration January 20, Leave a Reply Cancel reply Your email address will not be published.A transistor is a semiconductor device used to amplify or switch electronic signals and electrical power.

Or A transistor is a device that regulates current or voltage flow and acts as a switch or gate for electronic signals. Transistors consist of three layers of a semiconductor material, each capable of carrying a current.

In this section, you will see how semi-conductive materials are used to form a BJT, and you will learn the standard BJT symbols. Physical representations of the two types of BJT are shown in above Fig. A wire lead connects to each of the three regions,are shown. These leads are labeled E,B and C for emitter,base and collector,respectively. The base region is lightly doped and very thin compared to the heavily doped emitter and the moderately doped collector region.

The reason for this is discussed in the next section. Notice that the both cases the base-emitter BE junction is forward-biased and the base collector BC junction is reverse-biased. The base has a low density of holes, which are the majority carriers,as represented by the white circles.

A small percentage of the total number of free electrons injected into the base region recombine with the holes and move as valence electrons through the base region and into the emitter region as hole current,indicated by the red arrows.

When the electrons that have recombined with holes as valence electrons leave the crystalline structure of the base,they become free electrons in the metallic base lead and produce the external base current. Most of the free electrons that have entered the base do not recombine with holes because the base is very thin.

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A s the free electrons move toward the reverse-biased BC junction,they are swept across into the collector region by the attraction of the positive collector supply voltage.

The free electrons move through the collector region, into the external circuit,and then return into the emitter region along with the base current,as indicated. Watch also how transistor work? Notice that the arrow on the emitter inside the transistor symbols points in the direction of conventional current. These diagrams show that the emitter current I E is the sum of the collector current I C and the base current I Bexpressed as follow:. The capital-letter subscripts indicate dc values.

Finally, maximum ratings of a BJT are discussed. Although in this chapter we are using separate battery symbols to re[present the bias voltages, in practice the voltages are often derived from a single de power supply.Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts.

It only takes a minute to sign up. Lets say you want to operate at 20uA base current. To move along that 20uA graph, you need to vary Vce. But to vary Vce, you either vary Vb voltage at base or change the values of the resistors at emitter or collector or the Vc voltage at collectoris this correct? You are correct in your assumption that to vary Vce you must adjust the resistor values. The equation for the collector current Ic is as follows:.

We know that beta and base current are generally constant in your questionso as long as Vcc is also constant the only variable that you can adjust is the resistance. Sign up to join this community. The best answers are voted up and rise to the top.

Asked 2 years, 2 months ago. Active 1 month ago. Viewed times. Improve this question. To the extent that the collector current is constant, you can vary the collector voltage at will and the collector current won't change.

Bipolar junction transistor(BJT):Applications & characteristics

This is the max collect current? But for a fixed base current, between 20 to 80uA, none of them can give this max collector current The meaning of the y-intercept of this load line awaits a clarity not yet provided from you.

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Make each question self-contained. Active Oldest Votes. Improve this answer. Burritos Burritos 83 7 7 bronze badges. Of course the first sentence is not wrong - however, it does not reflect practical aplication aspects.One of the more useful BJT device plots is the family of collector curves.

A DC power supply is attached from the collector to emitter and then swept from zero volts to some upper value. Simultaneously, we track the resulting collector current and plot the result. This results in one trace.

The base current is then increased and the DC supply swept again for a second trace. This process is repeated to create a family of curves. Ideally, the corresponding collector current would be 0 but a small leakage current occurs. The curves above this correspond to increasing levels of base current; each new base current stepping up a fixed amount for each subsequent trace e.

The most striking thing about this set of curves is that there are three distinct regions or zones of operation. To the extreme left of the curve the current rises rapidly. This is known as the saturation region. The break-over point is fairly small at just a few tenths of a volt. The saturation region is used in transistor switching applications. At the extreme right is another region where the collector current rises rapidly.

This is called the breakdown region. This is the same effect we saw with individual diodes. We do not wish to operate devices in this region as damage may result. For general purpose devices this will be in the range of 30 to 60 volts or so, but it can be much higher.

In between these two extremes is a region where the collector current is relatively constant, showing only a modest positive slope. This is the constant current region. This is where we want the transistor to operate for applications such as linear amplifiers. A device called a curve tracer can be used to generate this family of curves in the lab. We then find the nearest plot line to that point. We count the number of traces and multiply by the base current step size to determine the corresponding base current.God would "destroy the churches wholesale and the church members by the millions.

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4.3: BJT Collector Curves

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Transistors (BJT) - Characteristic Curve #4

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bjt transistor characteristic curves

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