Structure and use of pnp transistor, Electrical Engineering

Structure and use of PNP transistor:

The figure opposite is a schematic presentation of a PNP transistor related to two voltage sources. To construct the transistor conduct appreciable current (on the order of 1 mA) from E to C, VEB have to be above a minimum value occasionally considered to like the cut-in voltage. The cut-in voltage is generally about 600 mV for silicon BJTs at room temperature but can be different depending upon the type of transistor and its biasing. This applied voltage results the upper P-N junction to 'turn-on' permitting a flow of holes from the emitter into the base. In active mode, the electric field lay between the emitter and the collector (caused by VCE) causes the majority of these holes to cross the lower P-N junction into the collector to make the collector current IC. The remainder of the holes again combines with electrons, the majority carriers in the base, forming a current through the base connection to make the base current, IB. As displayed in the diagram, the emitter current, IE, is the total transistor current that is the sum of the other terminal currents (that is., IB=IB+IC).

In the figure, the arrows presenting current point in the direction of conventional current - the flow of holes is in similar direction of the arrows since holes carry positive electric charge. The ratio of the collector current to the base current is termed as the DC current gain, in active mode. This gain is generally 100 or more, but robust circuit designs do not depend upon the exact value. The value of this gain for DC signals is considered to as hFE, and the value of this gain for AC signals is considered to as hfe. Though, when there is no specific frequency range of interest, the symbol β is employed.

It should as well be noted that the emitter current is related to VEB exponentially. At room temperature, increment in VEB by approximately 60 mV increases the emitter current by a factor of 10. Since the base current is approximately proportional to the collector and emitter currents, they vary in similar way.

Posted Date: 1/10/2013 6:52:06 AM | Location : United States







Related Discussions:- Structure and use of pnp transistor, Assignment Help, Ask Question on Structure and use of pnp transistor, Get Answer, Expert's Help, Structure and use of pnp transistor Discussions

Write discussion on Structure and use of pnp transistor
Your posts are moderated
Related Questions
If a compressor in a system can change a message crest factor from 3.2 to 2, while maintaining its peak amplitude constant, find the decibels of improvement in signal-to-noise rati

Q. Briefly explain about Laplace transform? Many commonly encountered excitations can be represented by exponential functions. The differential equations describing the network

Q. Sampling of digital communication systems? Sampling of an analog signal makes it discrete in time. A bandlimited signal can be recovered exactly from its samples, taken peri

Q. Why FET is called a voltage-controlled device? Why its input resistance is high? In the case of a FET the output current ID is a function of the voltage VGS applied to the i

The energy consumption for a small factory is given at the end of the brief. a) Three commercial tariffs from an energy supplier are shown below. Using these (or other commercia

deriving formula of the frictional force

Electronic voltage regulators: Electronic voltage regulators operate through comparing the actual output voltage to a few internal fixed reference voltages. Any type of differ

Q. What is an oscillator? Discuss the advantages of Oscillators ? An oscillator is a system consisting of active and passive circuit elements to produce a sinusoidal or other r

Branch Operations Normally  the program  executes in  a sequence. The contents of the program counter register are incremented by  one during  the execution  of current  instr

what are the different digital modulation techniques?