Bipolar Transistors Transistor Switching Circuits Volt-Ampere Characteristics of BPT

Transistors

Bipolar, field, JGBT.

Bipolar transistors
The bipolar transistor is a semiconductor three-layer npn or pnp structure and is designed to amplify the power of electrical signals.
The scheme of the technological structure of the bipolar transistor and its symbols are shown in fig. one.


Fig. 1 Schemes of technological structures of bipolar transistors
and their conventions.

The internal structure of the transistor


Wiring transistor
These three layers have the following names: emitter (E), base (B), collector (K). To enhance the electrical power, three options are used to turn on the bipolar transistor: with a common emitter (OE), a common base (ON) and a common collector (OK).


Figure 2 Wiring transistor

Modes of operation of the transistor
1. Active (booster)
2. Saturation mode
3. Cutoff mode

Tatic current-voltage characteristics of BPT


Pic 3


Amplification properties of the transistor


common emitter transistor circuit

Proof: let


The transistor is controlled by the base current

The replacement circuit of a bipolar transistor


Pic 4

The relationship between input and output currents and voltages in the transistor, presented in the form of an equivalent quadrupole, is expressed by the system of equations of the electrical state:



h - transistor parameters

transistor input resistance


feedback ratio


DC gain


output conductivity


One of the main parameters of a bipolar transistor is the current transfer ratio. When operating in DC mode for a common base circuit, this is the ratio of the collector current to the emitter current



For a common emitter circuit, the current transfer ratio in DC mode is equal to the ratio of the collector current to the base current



In addition, as in the quadrupole, the transistor other main parameters are the input and output resistances, which characterize the consistency of the input and output circuits of the transistor with other quadripoles.
Graphic definition of h - transistor parameters

Uke = Ek - Ik • Rk - line load



Table 1 shows the comparative parameters of these inclusion schemes.