It’s a model to describe large signal behaviour of a transistor, and start with the simple notion of two back to back diodes. For example the diodes seen at the two . It can be shown that (see S.M. Sze, Physics of Semiconductor Devices), therefore . where. More Complete Ebers-Moll Model. Model includes configurational. Ideal transistor model. Forward active mode of operation General bias modes of a bipolar transistor The Ebers-Moll model Saturation.

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That is, a PNP transistor is “on” when its base is pulled low relative to the emitter. In contrast, unipolar transistors, such as field-effect transistorsonly use one kind of charge carrier.

A significant ebrrs are also now made from gallium arsenideespecially for mode high speed applications see HBT, below. Charge flow in a BJT is due to diffusion of charge carriers across a junction between two regions of different charge concentrations. The base transport factor equals: As shown in the diagram, the emitter current, I Eis the total transistor current, which is the sum of the other terminal currents, i.

Finally, there is the reverse active mode of operation. Please help improve it to make it understandable to non-expertswithout removing the technical details. The thin shared base and asymmetric collector—emitter doping are what differentiates a bipolar transistor from two separate and oppositely biased diodes connected in series. The thermal runaway process associated with secondary breakdown, once triggered, moodel almost instantly and may catastrophically damage the transistor package.


Bipolar junction transistor

A combination of equations 5. By design, most of the BJT collector current is due to the flow of charge carriers electrons or holes injected from a high-concentration emitter into the base where they are minority ebfrs that diffuse toward the collector, and so BJTs are classified as minority-carrier devices.

For DC conditions they are specified in upper-case.

When a eners is used at higher frequencies, the fundamental limitation is the time it takes the carriers to diffuse across the base region The collector—emitter current can be viewed as being controlled by the base—emitter current current controlor by the base—emitter voltage voltage control. A BJT consists of three differently doped semiconductor regions: When the device is in forward active or forward saturated mode, the arrow, placed on the emitter leg, points moddl the direction of the conventional current.

The Bipolar Transistor (Ebers Moll Model)

This page was modwl edited on 31 Decemberat While this boundary condition is mathematically equivalent to that of an ideal contact, there is an important difference.

The emitter efficiency defined by equation 5.

Modern Semiconductor Devices for Integrated Circuits. The current sources quantify the transport of minority carriers through the base region. Since the carrier lifetime can be significantly longer than the base transit time, the turn-off delay causes a large and undesirable asymmetry mode turn-on and turn-off time. And the emitter current due to electrons, I E,nsimplifies to: The result is that the transistor makes a good switch that is controlled by its base input.


That drift component of transport aids the normal diffusive transport, increasing the frequency response of the transistor by shortening the transit time across the base.

Bipolar junction transistor – Wikipedia

When the base—collector midel reaches a certain device-specific value, the base—collector depletion region boundary meets the base—emitter depletion region boundary. The electrons in the base are called minority carriers because the base is doped p-type, which makes holes the majority carrier in the base.

Calculate the saturation voltage of a bipolar transistor biased with a base current of 1 mA and a collector current of 10 mA.

This is called conventional current. Simplified cross section of a planar NPN bipolar junction transistor.

In this “on” state, current flows from the collector to the emitter of the transistor. The BJT when operated in normal mode and inverse mode is shown in the figure below. The model contains two diodes and two current modek as shown in Figure 5.

In other projects Wikimedia Commons. In this mode, the transistor has an emitter efficiency and base transport factor as described by equations 5. The Art of Electronics 2nd ed.

It is common in modern ultrafast circuits, mostly RF systems.