Introduction:Figure below exhibits the characteristics of n-type and p-type and improvement mode MOS transistors. The polarity of currents and voltages are shown for both types of transistor. This can be observed that the voltages are positive in n-type and negative in p-type (comprising the threshold voltage). It can also be seen that current flow through the transistors is from drain to source in the n-type device but from source to drain in the p-type device.The circuits that are of interest, which execute from a single-rail supply, the p-type device will appear upside-down in circuit configuration with respect to n-type device. If the convention is adopted for the p-type device to use the source-to-gate voltage, VSG, and the source-to-drain voltage, VSD, as shown in figure below, then the similar set of equations can be employed to characterise both improvement mode devices where all voltages, comprising the threshold voltage VT are considered positive.
Figure: Sign Conventions for n-type and p-type MOS Transistor
Figure: Characteristics of both kinds of MOS Transistors
Current-Voltage Relationships:A conducting channel is made in the improvement-mode device if VGS > VT. When the above sign convention is adhered to, the similar set of equations can be employed to explain the current-voltage relationship for both p-type and n-type transistors.Non-Saturation Region:n-channel:ID = Kn [2(VGS - VT) VDS – V2DS]p-channel:ID = Kp [2(VGS - VT)VSD – V2SD]Saturation Region:n-channel:ID = Kn (VGS - VT)2p-channel:ID = Kp (VSG - VT)2The CMOS Inverter:The CMOS inverter is made by joining a p-type and n-type transistor and a transistor in series, with the p-type inverted to execute from a single-voltage supply, as shown in figure below. The transfer characteristic of inverter is too shown. The critical logic voltages, stated at the points on the characteristic where the slope is -1, can be adjusted by modifying the relative aspect ratios W/L of the two transistors. Usually they are set at 20 to 25% and 75 to 80% of the supply voltage.When the nominal logic voltages are stated as VL = 0V and VH = VDD then:
When the input voltage is LO with Vi = 0V the gate-source voltage of lower n-type transistor, T1, is zero that is below the threshold voltage, VT, and therefore this transistor is non-conducting or OFF. On other hand, the p-type transistor, T2, that is upside down, has a VGS = -VDD or VSG = VDD that is well above the threshold voltage and therefore this transistor is completely conducting or ON. Transistor T2 can then supply current to any load needed and with full conduction will give an output voltage VO → VDD or the logic HI level. Whenever the input voltage is HI with Vi = VDD the gate-source voltage of p-type transistor is zero and hence T2 is OFF, whereas the gate-source voltage of the n-type transistor is equivalent to VDD and therefore transistor, T1, is completely conducting and is ON. With an adequately high trans conductance parameter the output voltage can be made much low and hence VO → 0V or logic LO. This outcome in an inverting action is confirmed by the table shown below:
INPUT T1 T2 OUTPUT
Vi = 0V, LO OFF ON Vo → VDD, HI
Vi = VDD, HI ON OFF Vo → 0V, LO
Figure: Schematic figure and Transfer Characteristic of a CMOS Inverter
The CMOS NOR Gate:The schematic figure of a 2-input CMOS NOR gate is as shown in figure below. It can be seen that the transistors are driven in p-type cum n-type pairs through each input. Basically, the n-type driving transistors are joined in parallel whereas the p-type load transistors are joined in series. In each pair, either the n-type transistor will be ON whereas the p-type is OFF, or vice-versa, based on the logic state of the related input. The table of conduction states for all transistors can be drawn up to establish the logic function executed by the gate, as shown below. The state of output can be established by treating the transistors that are ON as equivalent to closed switches and those which are OFF as equal to open switches. This is as shown, for example, in figure below for case where Input A is HI and Input B is LO.
IN A IN B T1 T2 T3 T4 OUT
LO LO OFF ON OFF ON HI
LO HI OFF ON ON OFF LO
HI LO ON OFF OFF ON LO
HI HI ON OFF ON OFF LO
The CMOS NAND Gate:The schematic figure of a 2-input CMOS NAND gate is as shown in figure below. This can be seen that the structure is identical to the NOR gate, however in this case the n-type driving transistors are joined in series whereas the p-type load transistors are joined in parallel. Transistors are again driven in n-type cum p-type pairs with one transistor ON whereas the other is OFF. The table of conducting states of transistors for all logic combinations of the inputs is shown below. The switch equivalent is as shown for the case where Input A is HI and Input B is LO in figure below.
LO HI OFF ON ON OFF HI
HI LO ON OFF OFF ON HI
Figure: Schematic figure of a 2-input CMOS NOR Gate
Figure: Equivalent Circuit of NOR Gate with IN A = HI and IN B = LO
Figure: Diagram of a 2-input CMOS NAND Gate
Figure: Equivalent Circuit of the NAND Gate with IN A = HI and IN B = LO
Latest technology based Electrical Engineering Online Tutoring Assistance
Tutors, at the www.tutorsglobe.com, take pledge to provide full satisfaction and assurance in Electrical Engineering help via online tutoring. Students are getting 100% satisfaction by online tutors across the globe. Here you can get homework help for Electrical Engineering, project ideas and tutorials. We provide email based Electrical Engineering help. You can join us to ask queries 24x7 with live, experienced and qualified online tutors specialized in Electrical Engineering. Through Online Tutoring, you would be able to complete your homework or assignments at your home. Tutors at the TutorsGlobe are committed to provide the best quality online tutoring assistance for Electrical Engineering Homework help and assignment help services. They use their experience, as they have solved thousands of the Electrical Engineering assignments, which may help you to solve your complex issues of Electrical Engineering. TutorsGlobe assure for the best quality compliance to your homework. Compromise with quality is not in our dictionary. If we feel that we are not able to provide the homework help as per the deadline or given instruction by the student, we refund the money of the student without any delay.
www.tutorsglobe.com offers languages and reliability homework help, assignment help, case study, writing homework help, online tutoring assistance by computer science tutors.
a centrifugal pump is a device which imparts energy to a fluid. this energy infusion can reason a liquid to flow, increases to a higher level, or both.
www.tutorsglobe.com offers answering questions to total expenditure and price elasticity, calculate total expenditure, and price elasticity - economics assignment help- homework help.
Introduction to Genetics tutorial all along with the key concepts of History of Genetics, Gregor Mendel discovery, sex-linked inheritance of white eye, polymerase chain reaction and Importance of genetics
tutorsglobe.com analysing and interpreting financial statements part ii assignment help-homework help by online financial accounting tutors.
Coordination in Animals tutorial all along with the key concepts of Neuron, Importance of Coordination and Sensory Receptors
Theory and lecture notes of Risk Sharing in Contingent-Claims Market all along with the key concepts of Budget Line, Iso-Expected Value Line, Choices of Decision-makers, Indifference Curves with Risk Averseness. Tutorsglobe offers homework help, assignment help and tutor’s assistance on risk sharing in contingent-claims market.
Classifications of Amino Acids tutorial all along with the key concepts of Criteria for Classification of Amino Acids, Classification Based on Structure, Categorization Based on Polarity, Categorization Based on Nutritional Requirements
www.tutorsglobe.com offers coordination compounds homework help, coordination compounds assignment help, online tutoring assistance, inorganic chemistry solutions by online qualified tutor's help. coordination compounds
Classes, structures and naming of Alcohols tutorial all along with the key concepts of Classes of Alcohols, Monohydric, Dihydric, Trihydric, Primary alcohol, Secondary alcohol, Tertiary alcohol, Naming Alcohols and Physical Properties of Alcohols
Basic Petroleum refining tutorial all along with the key concepts of Separation into Components, Fractional Distillation and Vacuum Distillation, Absorption and Stripping, Solvent Extraction and Adsorption, Thermal Diffusion and Crystallization, Cracking and Fluid Catalytic Cracking
Financial reporting has been about for many hundreds of years. It appears to have come out like a result of one or more persons having custody and management of assets that belonging to one or more others.
Calorimetry tutorial all along with the key concepts of Heat and temperature, Specific heat capacity and latent heats, Experimental methods of Calorimetry and Applications of Calorimetry
modern periodic law tutorial all along with the key concepts of long form of the periodic table, nomenclature of elements
tutorsglobe.com example for demand function assignment help-homework help by online demand tutors
1953598
Questions Asked
3689
Tutors
1482733
Questions Answered
Start Excelling in your courses, Ask an Expert and get answers for your homework and assignments!!