Advantages of bjt over mosfet, Electrical Engineering

Assignment Help:

Advantages of BJT over MOSFET:

BJTs have some benefits over MOSFETs for at least two digital applications. Very first, in high speed switching, they do not comprises the "larger" capacitance from gate, which while multiplied by the resistance of the channel provides the intrinsic time constant of the process. The intrinsic time constant places a boundary on the speed a MOSFET can operate at since higher frequency signals are filtered out. Widening the channel decreases the resistance of channel, but raises the capacitance by closely the same amount. Reducing the width of the channel increases the resistance, but decreases the capacitance by similar amount. R*C=Tc1, 0.5R*2C=Tc1, 2R*0.5C=Tc1. There is no way to minimize the intrinsic time constant for a specific process. Different processes by using different gate thicknesses, channel lengths, channel heights, and materials will have different intrinsic time constants. This problem is mostly prevented with a BJT as it does not have a gate.

The 2nd application in which BJTs have a benefit over MOSFETs stems from the first. While driving several other gates, called fan out, the resistance of the MOSFET is in series along with the gate capacitances of the other FETs, making a secondary time constant. Delay circuits make use of this fact to make a fixed signal delay by using a small CMOS device to send a signal to many other, several times larger CMOS devices. The secondary time constant could be minimized by raising the driving FET's channel width to reduce its resistance and decreasing the channel widths of the FETs being driven, reducing their capacitance. The drawback is that it raises the capacitance of the driving FET and increases the resistance of the FETs being driven, but generally these drawbacks are a minimal problem when as compared to the timing problem. BJTs are better capable to drive the other gates because they can output more current than MOSFETs, permitting for the FETs being driven to charge faster. Several chips use MOSFET inputs and BiCMOS outputs.


Related Discussions:- Advantages of bjt over mosfet

Dc charging and discharging circuit, The circuit shown below is a DC chargi...

The circuit shown below is a DC charging and discharging circuit. a.  At t = 0 sec, switch S1 is thrown to position 1 ("pos1"). Write the mathematical expressions for and .

PSpice Project, I would send the project file so you can take a look at it....

I would send the project file so you can take a look at it.

Complex number and variabls, what is tha lapelace transform of t^n please g...

what is tha lapelace transform of t^n please give me the answer i am so worried about iy???

3-phase 4 wire meters with ct and md, 3-Phase 4 Wire Meters with CT and MD ...

3-Phase 4 Wire Meters with CT and MD If load is commonly more than 50 A, CT operated meters should be used. It is to be remembered that CTs should be properly selected for acc

Power spectral density, Power Spectral Density: To introduce the P...

Power Spectral Density: To introduce the Power Spectral Density (PSD) of a random signal. To study classical methods for PSD estimation. To investigate model-based

Electronic voltage regulators, Electronic voltage regulators: Electron...

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

Impedance heating system, Under what circumstances is individual circuit pr...

Under what circumstances is individual circuit protection for a lighting and applications panel board not required? What is the purpose of guarding runway contact conductors and

Working of r digital to analog converter, 2 n -R D/A CONVERTER An n-bit...

2 n -R D/A CONVERTER An n-bit 2 n -R D/A converter needs 2 n resistors of equal value R and (2 n+1 -2) analog switches. A 3-bit 2 n -R D/A converter is shown in Figure, which

Microcontroller interfacing, The conveyor system is driven by a 240 Volt 50...

The conveyor system is driven by a 240 Volt 50 Hz AC motor requiring a continuous 1 Amp supply. The conveyor has single direction operation. The loading mechanism for the winder

Two-winding distribution transformer, Q. A single-phase, 10-kVA, 2300:230-V...

Q. A single-phase, 10-kVA, 2300:230-V, 60-Hz, two-winding distribution transformer is connected as an auto transformer to step up the voltage from 2300 V to 2530 V. (a) Draw a s

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd