Assignment
Submitted To: Muhammad Farrukh Qureshi
To be filled by the student
To be filled by the lecturer
Assignment No:
01
Subject:
Electronic devices and cicuit
Topic / Title:
Hybrid equivalent of BJT
_ Total Marks: ………………..……….
Submitted By:
Abdullah mehmood
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SAP ID No:
11103
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Class (Program):
EE
Batch & Section:
Section A
Date Of Issue:-
_
Marks Obtained: ……...……………..
Date Of Submission:
Comments for Guidance
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Department Of Electrical Engineering (DEE)
Faculty of Engineering & Applied Sciences (FEAS)
Riphah International University (RIU), Islamabad
Hybrid Equivalent Model of BJT:
The Hybrid pi model of a BJT is a little sign model, named after the "
"- like comparable circuit for a bipolar
intersection semiconductor. It comprises of an information impedance, r , a yield impedance r0, and a voltage
controlled current source depicted by the trans conductance, gm. What's more it contains the base-producer
capacitances, the intersection capacitance, Cj,BE, and the dispersion capacitance, Cd,BE, and the base-authority
intersection capacitance, Cj,BC, likewise alluded to as the Miller capacitance.
The trans conductance, gm, of a bipolar semiconductor is characterized as the adjustment in the
gatherer current partitioned by the difference in the base-producer voltage.
The base input resistance r , is characterized as the difference in the producer base voltage
isolated by the difference in the base current.
The output resistance, ro, is defined as:
The base-emitter and base-collector junction capacitances are given by:
for the situation where the base-producer and base-gatherer intersections are sudden. Since the base-producer is
firmly forward one-sided in the forward dynamic method of activity, one needs to likewise incorporate the
dispersion capacitance of the base:
In view of the little sign model we would now be able to ascertain the little sign current addition versus
recurrence, hfe, of a BJT one-sided in the forward dynamic mode and associated in a typical producer setup. The
greatest current addition is determined while shorting the yield, coming about in:
The unity gain frequency, fT, also called the transit frequency is obtained by setting the small signal current gain,
hfe, equals to one, resulting in:
This transit frequency can be expressed as a function of the transit time,
Where the transit time,
:
, equals:
The circuit model subsequently incorporates the charging season of the base-producer capacitance,
as the base travel time,B, however not the travel season of the transporters through the base-authority
consumption region,C.
The collector transit time was presented and described by equations, which is repeated here:
The total transit time then becomes:
as well
The comparing travel recurrence, fT, can in any case be determined. While the solidarity acquire recurrence, fT, is
a significant figure of value of a bipolar semiconductor, another considerably more significant figure of
legitimacy is the greatest wavering recurrence, fMAX. This figure of legitimacy predicts the solidarity power
acquire recurrence and subsequently demonstrates the most extreme recurrence at which helpful force gain can be
considered typical from a gadget. The greatest wavering recurrence, fMAX, is connected to the travel recurrence,
fT, and is gotten from:
Where RB is the absolute base obstruction and Cj,BC is the base-authority capacitance. The complete base
opposition comprises of the arrangement association of metal-semiconductor contact obstruction, the opposition
between the base contact metal and the producer and the inborn base opposition.
Accepting a base contact, which is longer than the entrance profundity this base obstruction rises to
For an uneven base contact, where Rs,c, Rs,BE and Rs are the sheet protections under the base contact, between
the base contact and the producer and under the producer separately. Ls,E is the producer stripe length of the
producer, Ws,E is the producer stripe width of the producer and
Is the arrangement distance between the base contact and producer? For a twofold sided base contact, the all-out
base opposition approaches
The base-collector capacitance equals: