Electronics Devices And Circuits (Boylestad et. al.) Chapter 4 "Transistor Biasing", Slides of Electronics

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Any increase in

alternating current

voltage, current, or

power is the result of

energy transfer from

the applied dc

supplies.

Region of the BJT Characteristic Linear- Region Operation Cut-off Region Operation Saturation Region Operation

Base-Emitter Junction forward-biased

Base-Cllector Junction reverse biased

Base-Emitter Junction reverse-biased

Base-Collector Junction reverse-biased

Base-Emitter Junction forward-biased

Base-Collector Junction forward-biased

Loop

Transistor Saturation is used to describe any system in which levels have reached their maximum values.

Emitter-Bias The dc bias network includes an emitter resistor to improve the stability of the fixed- bias configuration. The more stable the configuration, the less responsive it is to unwanted changes in temperature and parameter variations.

This loop can be redrawn, Apply

Kirchoff's Voltage Law around on the

indicated loop in clockwise direction

with the resulting equation of:

Collector-Emitter

Load-Line The maximum collector current or collector saturation level for an emitter-bias design can be determined using the same method as for a fixed- bias configuration: Apply a short circuit between the collector-emitter terminals and calculate the resulting collector current:

Voltage-Divider Bias

In this picture, the voltage-diivider bias configuration is such a

network. When exact basis analyzed, the beta will be quite

small due to the changes into its sensitivityy. When the cicuit

were properly chosen, the resulting levels of ICQ and VECQ will

be almost independent of beta.

• Exact Analysis Method

2. Approximate Method