Thursday, March 19, 2015

IMPORTANT POINTS IN ELECTRICAL ENGINEERING

> data routing
> data selection
> parallel to serial converter

->For changing Q point dont vary load as gain is effected and dont vary feedback as stabilities effected. 
 -> we want feedback for DC and dont want feedback for AC.


-> In continuous signals limit included in both where as in discrete the limit is not included in both. 
-> System is physically defined as combination of physical elements which produces expected output with the available input.

-> system is defined as transfer function which is the ratio of output by input.

-> ratio of laplace transform of output by laplace transform with inital conditions '0'.
-> almost all systems will not have initial conditions zero. 
-> analysis is based on transfer function may prove the system is stable even if internal components are exceeding their ratings.
-> transfer function gives overall status of system but not internal states of the system .
-> It is very difficult to analyse MIMO using transfer function .

REMEDY: state variable technique for all analysys and
synthesis.

-> a system is defined as impulse response.
-> any linear system is described by integral differential equation i.e. nth order differential equation between input and output mathematically


note: analysis of system is by differentiation .but sysnthesis of system is by differentiation.


-> any transform is to convert integral differential equation into linear algebra to ease the analysis.


-> system can also have be defined as an operators which maps the input and output. 



-> arrow shows convetional current direction when the junction is forward biased for any device.

-> NOR requres more gates and power dissipation is also more and hence NAND is preferrd to NOR.


-> BJT is a device used as amplifier and switch by the process of transfer of resistance from emitter junction to collector junction using majority and minority carriers.


-> back to back connection of two diodes can be treated as transistor .but can never work as transistor because doping and size of each.


-> CC amplifier is must for impedence matching 

-> by default common emitter is taken 



-> Ge requires less voltage than silicon radius is large 
-> NPN is preferred to PNP because of mobility is large for NPN.


-> In general biasing is defined as forward bias emitter junction and reverse bias collector junction . so that transistor is operated in active region and act as amplifier.
-> DC characterstics does not give a direct relation between output voltage and output. therefore, we need a DC load line.


-> DC load line is also a straight line that passes through
Q.point but with AC slope. 



RANDOM: a signal is said to be random signal if the amplitude is not known at certain timings i.e. it is not known completely and it is not unknown completely. 


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