6.4 MOSFET Switch Implementation of Logic Gates

• S circuit model of NAND Gate

• S circuit model of n-channel MOSFET inverter

• MOSFET inverter

6.3 MOSFET and its S model

• MOSFET belongs to transistor class, with three terminals: control, input & output
• Control = Gate, Input = Drain, Output = Source

• VGS, IDS, VDS

• S model of MOSFET

A typical value for VT of n channel MOSFET is 0.7 V

6.2 Logic Functions using Switches

Switches implement a form of digital logic called steering logic

6.1 The Switch

5.6 Number Representation

• Value of binary number AnAn-1...A2A1A0 :

5.5 Simplifying Logic Expressions

• Rules

• De Morgan's law:

5.4 Standard Sum-of-Products Representation

• Logic expressions in the sum-of-products form are represented using two levels of operations as a set of product (AND) terms, each comprising one or more variables in their true forms (for example, A) or complement forms (e.g., A), combined using the OR function

• We can write a sum-of-products expression from a truth table representation by first writing a product term for each row in the truth table with a 1 in its output column, and then summing these product terms. Each product term comprises an AND function of all the input variables. A variable will appear in its true or complement form in a product term corresponding to a given row in the truth table depending on whether it appears as a 1 or a 0 in that row