Notes Covering Field-Effect Transistors



Notes Covering Field-Effect Transistors

Introduction

Bipolar transistor - elektropreobrazovatelny semiconductor device with one or more electric transitions, designed to enhance, transform, and generate electrical signals. The device is planar bipolar transistor is shown. All construction is performed on the wafer of silicon or germanium or other semiconductor, which are three areas with different types of conductivity. The figure type transistor npn, whose average area of ??a hole, and with the electronic conductivity of the extreme (Horowitz, 2006, 33-45).

The average area is called the base, one of the most extreme areas - emitter, the other - a collector. Accordingly, in the two-transistor pn-junction: the emitter - between the base and emitter and collector - between the base and collector. Scope base must be very thin, much thinner than the emitter and collector regions (shown in the figure is disproportionate.) On this depends the condition of good work of the transistor. The transistor operates in three modes depending on the voltage on its transitions. When operating in active mode at the emitter junction voltage directly on the collector the opposite (Horowitz, 2006, 33-45). In the cut-off for both transitions filed a reverse voltage. If these transitions to file a direct voltage, the transistor will operate in the saturation regime.

Field-Effect Transistors (FETs)

MOSFETs are called active semiconductor devices in which the output current is controlled with an electric field (in the bipolar transistor output current is controlled by input current). FETs are also called unipolar, as in the flow of electric current is involved only one type of media. There are two types of field-effect transistors: a control junction and insulated-gate. They all have three electrodes: source (the source of the carriers), gate (control electrode) and sink (electrode, which drains the carriers). Transistor with a control p - n-junction. His schematic representation is shown in Fig. 1.21, and a conditional graphic symbol of the transistor - in Fig. 1.22, b (p - and n-type, respectively). The arrow indicates the direction from layer to layer p n (as an arrow in the image of the emitter bipolar transistor). In the linear dimensions of integrated circuit transistors can be significantly less than 1 micron (Horowitz, 2006, 33-45).

In Fig. 1.22 The unit transistor

In Fig. 1.23 Graphical representation of a - p-channel type, b - n-type channel

The resistivity of layer n (gate) is much smaller than the resistivity p layer (channel), so the area of p-n-junction, depleted of mobile charge carriers and having a very large resistivity, located mainly in layer p. If the conductivity type semiconductor layer transistor in the above change to the opposite, then we get a field effect transistor with a control p-n-junction and the n-type channel. If a positive voltage is applied between the gate and source of the transistor with a channel p-type: su and> 0, then it will shift the p - n-move in the opposite direction. By increasing the reverse voltage across the junction, it expands mainly due to the channel (due to the above differences in resistivity) (Gibilisco, ...