Introduction to Digital Electronics

DC An electrical current can flow in either of two directions. If it flows in only one direction, it is called direct current (DC). A battery is an example of a DC voltage that can supply DC current! Electrical engineers also use the term DC to refer to an average (or constant part of) a voltage or current signal.

AC A current which alternates in direction or polarity is called an alternating current (AC). The current flowing from a wall outlet is an example of an AC current! DC voltage, RMS Voltage, Frequency, Period

Resistors

Resistor Color Code

Voltage Divider +VDD = Use Ohm’s Law, KCL, KVL! I2= 5 / (15K) = 0.33 mA I1= VDD / (R1 + R2) = 0.33 mA I1= 5 / (15K) = 0.33 mA Vout = [R1 / (R1 + R2)] * VDD Vout = 5/3 Volts

Capacitors There are many kinds of capacitors but they all do the same thing: store charge. The simplest kind of capacitor is two conductors separated by an insulating material.

Diodes A diode is like and electronic one-way valve. It will allow current to flow in only one direction! Clearly, diodes can be used to convert AC currents to DC!

Transistors Transistors are three terminal devices. A very small current or voltage at one terminal can control a much larger current flowing between the other two leads.

Operational Amplfier Operational Amplifiers take small voltages and make them MUCH larger. Golden Rules (Op amp with negative feedback): No-current flows into either (+) or (-) inputs. The (+) and (-) inputs are at the same voltage.

Digital Signals A digital signal can take on only one of two voltages: 0 Volts and 5 Volts. The Handy Board treats 0 Volts as logical TRUE and the 5 Volt signal as logical FALSE. 5 Volts 0 Volts

Analog Signals An analog voltage can take on any value between 0 and 5 Volts. An Analog-to-Digital Converter (ADC) within the Handy Board will, however, will quantize the analog signal. The HandyBoard ADC is 8 bits wide.

Gates The most basic digital devices are called gates. Gates got their name from their function of allowing or blocking (gating) the flow of digital information. A gate has one or more inputs and produces an output depending on the input(s). A gate is called a combinational circuit. Three most important gates are: AND, OR, NOT

Digital Logic Binary system -- 0 & 1, LOW & HIGH, negated and asserted. Basic building blocks -- AND, OR, NOT

ECE 301 - Digital Electronics Numbers ECE 301 - Digital Electronics

ECE 301 - Digital Electronics 52 What does this number represent? What does it mean? ECE 301 - Digital Electronics

ECE 301 - Digital Electronics 1011001.101 What does this number represent? Consider the base (or radix) of the number. ECE 301 - Digital Electronics

ECE 301 - Digital Electronics Binary Addition 0 0 1 1 + 0 + 1 + 0 + 1 0 1 1 10 Sum Carry ECE 301 - Digital Electronics

ECE 301 - Digital Electronics Binary Addition Examples: 01011011 + 01110010 11001101 10110101 + 01101100 00111100 + 10101010 ECE 301 - Digital Electronics

ECE 301 - Digital Electronics Binary Subtraction 0 10 1 1 - 0 - 1 - 0 - 1 0 1 1 0 Difference Borrow ECE 301 - Digital Electronics

ECE 301 - Digital Electronics Binary Subtraction Examples: 01110101 - 00110010 01000011 10110001 - 01101100 00111100 - 10101100 ECE 301 - Digital Electronics

Binary Multiplication 0 0 1 1 x 0 x 1 x 0 x 1 0 0 0 1 Product ECE 301 - Digital Electronics

Binary Multiplication Examples: 10110001 x 01101101 00111100 x 10101100 ECE 301 - Digital Electronics

DeMorgan’s Theorems Digital Electronics  2,1 Introduction to AOI Logic DeMorgan’s Theorems DeMorgan’s Theorems are two additional simplification techniques that can be used to simplify Boolean expressions. Again, the simpler the Boolean expression, the simpler the resulting logic. Introductory Slide / Overview of Presentation Project Lead The Way, Inc. Copyright 2009

DeMorgan’s Theorem #1 Proof 1 1 DeMorgan’s Theorems Digital Electronics  2,1 Introduction to AOI Logic DeMorgan’s Theorem #1 Proof Overview & proof of DeMorgan’s Theorem #1 1 1 The truth-tables are equal; therefore, the Boolean equations must be equal. Project Lead The Way, Inc. Copyright 2009

DeMorgan’s Theorem #2 Proof 1 1 DeMorgan’s Theorems Digital Electronics  2,1 Introduction to AOI Logic DeMorgan’s Theorem #2 Proof Overview & proof of DeMorgan’s Theorem #2 1 1 The truth-tables are equal; therefore, the Boolean equations must be equal. Project Lead The Way, Inc. Copyright 2009

Thank You Created By – Prof. Swapan Kumar Gupta SHD College,Pathankhali