Transistor bipolar junction

The bipolar junction transistor (BIT) consists of tliree layers doped n-p-n or p-n-p tliat constitute tire emitter, base and collector, respectively. This stmcture can be considered as two back-to-back p-n junctions. Under nonnal operation, tire emitter-base junction is forward biased to inject minority carriers into tire base region. For example, tire n type emitter injects electrons into a p type base. The electrons in tire base, now minority carriers, diffuse tlirough tire base layer. The base-collector junction is reverse biased and its electric field sweeps tire carriers diffusing tlirough tlie base into tlie collector. The BIT operates by transport of minority carriers, but botli electrons and holes contribute to tlie overall current. 

Figure C2.16.8. Schematic energy band diagram for an n-p-n bipolar junction transistor. Positions of quasi-Fenni levels and bias voltages are indicated.

As Figure 10 shows, the n—p—n bipolar junction transistor (BJT) may be regarded as two back-to-back p—n junctions separated by a thin base region (26,32,33). If external voltages are applied so that the base-emitter (BE) junction is forward biased and the base-coUector (BC) junction is reverse biased, electrons injected into the base from the emitter can travel to the base-coUector junction within their lifetime. If the time for minority carrier electrons to... 

Mosfets switch faster than BJTs (bipolar junction transistors). The transition times of a Mosfet can be about 10 to 50ns, as compared to a BJT s typical transition time of 100 to 150ns. But that also makes the spikes far more severe in the case of converters that use Mosfet switches, because of the much higher dl/dt they can generate in the critical trace sections of the PCB. 

Field-effect transistors (FETs) have dominated the semiconductor industry, largely displacing the earlier bipolar junction transistor (BJT) because of its negligible gate current and convenience in the design of integrated circuits. Figure 29 sketches how an FET works. 

Ryu,S., et al., 1800V, 3.8A Bipolar Junction Transistors in 4H-SiC, Technical Digest of 58th Device Research Conference, Denver, CO, June 19-21, 2000, pp. 133-134. 

Zhang, J., et al., A High Current Gain 4H-SiC NPN Power Bipolar Junction Transistor, IEEE Electron Device Letters, Vol. 24, No. 5, May 2003, pp. 327-329. 

Agarwal, A. K., et al., Large Area, 1.3 kV, 17A, Bipolar Junction Transistors in 4H-SiC, Proc. of the 15th Inti. Symposium on Power Semiconductor Devices and ICs. ISPSD 03, Cambridge, England, April 14-17, 2003, pp. 105-108. 

This is the characteristic family of curves for a 2N3904 NPN bipolar junction transistor. 

In this section we will investigate how the DC current gain (Hfe) of a bipolar junction transistor varies with DC bias collector current Icq, DC bias collector-emitter voltage Vceq, and temperature. We will use the basic circuit shown below for all simulations ... 

Many semiconductor manufacturers have data sheets and PSpice models available online for easy access by engineers. In this section we will show how to obtain those models so that we can use them in a simulation. The types of models we will show can be split into two types. The first type of models are primitives that use only a. model statement. Examples of these are diodes, bipolar junction transistors (BJT), and MOSFETs. The second type of models we will download are subcircuit models such as op-amps, IGBT s, Darlington transistors, and MOSFET subcircuit models. 

The next model we will look at is an NPN bipolar junction transistor. The model of Pf that may vary between 50 and 350 ... 

When an np rectifier is connected, through a shared p region, to a pn rectifier, we have a npn junction "triode" transistor, or bipolar junction transistor (BJT). This transistor can amplify signals, just as does the vacuum-tube triode, but by a totally different mechanism. 

Depiction of bipolar junction transistors (A) npn and (B) pnp, and their representation in common-base or grounded-base circuit diagrams (C) npn, and (D) pnp, with the signs for positive currents I and voltages V indicated. (E) Four-terminal "black box" representation of the common-base npn circuit. After applying a small voltage vE, one measures a small current iE on the left, and on the output side one measures an output voltage vc and an output current ic the base current iB is not measured, but inferred. 

Both bipolar junction transistors (BJTs) and field-effect transistors (FETs) are charge-control devices [15]. The functions of the emitter, base, and collector electrodes of the BJT are replaced by the source, drain, and gate... 

Central to electronics is the IV measurement—that is, the measurement of the electrical current I through a device, as a function of the electrical potential, or bias, or voltage V placed across it. Electrical devices are most often "passive" two-terminal devices (resistors, capacitors, inductors, rectifiers and diodes, NDR devices), or "active" three-terminal devices (triodes, bipolar junction transistors, or field-effect transistors (FET)). 

Bipolar junction transistors are based on an n-p-n or p-n-p junction sequence. One of the p-n junctions is reverse biased, which suppresses the current between the outer electrodes, commonly called emitter and collector. The middle layer, which is connected to a third electrode (base), is spatially very thin. Initiated by a small control current over the base electrode, charge carriers are injected over the forward biased p-n junction and minority carriers can flood directly over the reverse biased p-n junction. This causes an increased current between emitter and collector. In contrast to FETs, bipolar junction transistors are current controlled. 

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