文档介绍：Supplementary reading - Common emitter amplifier
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The purpose of this reading is to explain more about transistor bias and why a
common emitter (CE) amplifier produces a 180 degree phase change to the input
signal. Understanding this will give a better understanding of transistor operation –
particularly how ‘bias’ works. We will be looking at a BJT (Bipolar Junction
Transistor) in this reading but do kept in mind a CE amplifier can be made with any
other active device.
Figure 1 shows a simplified diagram of a CE amplifier.
Now the values that I have placed on the diagram in figure 1 are totally arbitrary and
at the same time realistic. What the actual operating voltages and currents are for a
particular transistor would be determined by referring the manufactures data sheets.
In figure one the base current is supplied by a separate battery and a resistor Rb. The
amount of base current (Ib) can be changed by varying Rb.
1
The collector of the transistor is connected to +9V via Rc. Though not shown the
emitter is connect to the negative side of the 9 volt supply.
So there are two supply voltages in this diagram – the bias voltage and the main
supply voltage of 9 volts. Can you tell if this transistor is connected the correct way
in this circuit in terms of the battery voltages?
Both power suppli