Power BJT | Bipolar Junction Transistor | Characteristics of Power BJT | Switching Characteristics of Power BJT | Delay Time | Storage Time | Fall Time |Rise Time | BJT |
-: Power BJT :-
Bipolar transistor is a 3 layer 2 junction NPN or PNP semiconductor device.With one p-region sandwiched by two n-regions ,shown fig.(a) n-p-n transistor is obtained. With two p-regions sandwiching one n-region shown in fig.(b) p-n-p transistor is obtained.
n-p-n type. p-n-p type.
The term bipolar converts that the current flows in the device is due to movement of holes and electrons. BJT has three terminal name Emitter(E), Collector(C) and Base (B). BJT is current controlled device.
n-p-n type. p-n-p type.
The term bipolar converts that the current flows in the device is due to movement of holes and electrons. BJT has three terminal name Emitter(E), Collector(C) and Base (B). BJT is current controlled device.
Characteristic of power BJT-
1-Input characteristics-The graph between base current IB and base emitter voltage VBE gives input characteristics.
2-Output characteristics-A graph between collector current IC and collector emitter voltage VCE gives output characteristics of transistor zero base current that is IB=0 and as VCE is increased a small leakage current exist as shown in figure.is the best current is increases from IB=0,IB1,IB2 etc. collector current also rises Shown in figure.
Switching characteristics of BJT-
When a base current is applied so transistor does not turn on instantly because of the presence of internal capstans figure shows the various switching waveform of an NPN power transistor with resistance load between collector and emitter and figure (a).
Delay time-when base emitter voltage VBE is applied, the bese current rises to IBS the IC remains to zero or equal to leakage current ICEO.
"The time at which collector current begins to rise is called delay time td. "
Rise time (tr)-the time at which collector current rises to steady state value ICS in time tr is called rise time.
Rise time depend upon time capacitance during rise time tr collector emitter voltage from Vcc to VCE. The transistor is ON and Saturated state the forward bias current is maintained.
Storage time (ts)-when the base emitter voltage VBE is removed at time t1, the collector current does not change for time ts called storage time.
Fall time (tf)-The time after the storage time is called fall time tf.
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