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close this bookRadio and Electronics (DED Philippinen, 66 p.)
close this folder11. ACTIVE COMPONENTS -2- / TRANSISTORS
close this folder11.2. CHARACTERISTICS OF TRANSISTORS
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Open this folder and view contents11.2.1 HANDLING OF CHARACTERISTICS OF TRANSISTORS

(introduction...)

If a technician wants to use transistor in a certain electronic device, he has to know first exactly how it will work under the conditions given in this very circuit. To make it possible to predict the function of such a transistor, the producers of transistors supply the users with so called “data sheets”.

Beside a lot of values given directly in those data sheets, they are also plotting the most important characteristics of the transistors.

FIELD OF CHARACTERISTICS

If we consider for a moment again our transistor we find our easily that there are four electrical factors on which it is depending on.

- the base-emitter voltage

VBE

- the base-current

IB

- the collector-emitter voltage

VCE, and

- the collector-current

IC

To make the relations between those factors more obvious, we find nowadays very often the so called

FOUR-QUADRANT-FIELD

Fig. 130 shows a plot of such a kind.


fig. 130

The four quadrants are called:

QUADRANT 3 - shows the relation between the base-current and the base-emitter voltage. This is always a graph very similar as the graph of a diode, only turned around, so that it fits into this part of the field. So the base and the emitter are connected to the input of the common-emitter-connection, the characteristics is called the INPUT-CHARACTERISTICS.

This term can be understood too if you think about the explanation of the function of a transistor, where the base current was described as the precondition for the collector current.

QUADRANT 1 - shows the relation of the collector-current and the collector-emitter-voltage. We can see it also as the representation of the resistance between collector and emitter. So this resistance is depending on the base current, there are different graphs, for different amounts of base-current. Because the collector and the emitter are connected to the output side of a common-emitter connection, the characterics shown in this quadrant are called OUTPUT-CHARACTERISTICS.

QUADRANT 2 - represents the relation between the collector-current and the base-current. This means, it shows the relation between one factor which is part of the input side of the circuit and another which is part of the output side. Therefore this graph is called the MUTUAL-CHARACTERISTICS.

QUADRANT 4 - is used very rarely and only its name shall be only mentioned here: FEEDBACK CHARACTERISTICS-