Functional Waveforms for Electronics

4/6/2017

Lesson 16 EET 150

Learning Objectives

 In this lesson you will:  see typical waveforms used in electronic circuits  learn how to identify these waveforms by their shape  identify the amplitudes of these waves  learn where these waves are used

 see what instruments can produce and measure waveforms

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Common Waveforms-Sine Wave

Sine Waveform 3 3 Characteristics

2 Amplitude Measures RMS 1 Peak Peak-to-peak value Peak v(t) 0 to Peak value

Amplitude Peak 1 Measured with zero reference 2

 3 Root Mean Square 3 0 2 4 6 8 10 (RMS) Value 0 t 10 Time 0.707 of Peak Value

RMS factor of 0.707 only valid for Sine waves

Sine waves used to test amplifiers

Common Waveforms-Sine Wave

Example What is peak-to-peak value of the waveform shown?

What is peak 1.414 value of the V RMS 2 Vp waveform shown?

4 Vpp What is RMS value of the waveform shown?

VRMS =0.707(2) VRMS = 1.414 V

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Common Waveforms-Sine Wave

Sine wave with DC offset DC offset Sine Waveform raises entire 6 6 wave above zero 4

2.5 Waveform v(t) 2 Symmetric about 2.5

Amplitude +2.5

0 DC offsets can

2 be either  3 positive or 0 2 4 6 8 10 negative 0 t 10 Time

Common Waveforms-Square Wave

Square Wave Voltage Measures 3 3 Peak-to-peak value

RMS 2 Peak value

1 Peak Peak Measured with zero s(t) to reference

0 Peak Amplitude

1 Root Mean Square (RMS) Value 2

 3 Equals peak value 3 0 2 4 6 8 10 0 t 10 Square wave can Time Be off set with DC

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Common Waveforms-Pulse Train

Pulse Train has only positive values Signal used in computer circuits.

For this signal, half period is on- half period off

Adding DC off set to square wave produces pulse

Common Waveforms-Pulse Train

Pulse Train 5 Voltage Measures

4 Peak-to-peak value RMS Peak value Peak 2 to Peak Peak Peak value = peak- s(t)

to-peak value Amplitude 0 Root Mean Square (RMS) Value

2 A  3 RMS  0 2 4 6 8 10 2 0 t 10 Tim e

A = peak amplitude value

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Common Waveforms-Ramp Waves

Ramp waves increase linearly, reset, then repeat

Ramp waves used to move trace in scopes

Used to control and sweep frequency linearly

Dc off set can move waveform up or down

Common Waveforms-Ramp Waves

8 Voltage Measures 8 Peak-to-peak value

4 Peak Peak value RMS Peak to Peak Peak value = peak-

v(t) 0 to-peak value Amplitude Root Mean Square 4 (RMS) Value A  8 8 RMS  0 3 6 9 12 15 3 0 t 15 Tim e

A = peak amplitude value

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Common Waveforms-Ramp Waves

Ramp wave with negative dc off set Negative Dc off set lowers half of wave below zero

3 v 6 V RMS value of off set wave not equal to wave without offset

Common Waveforms-Triangle Waves Triangle waves increase linearly then decrease linearly at a given frequency

Waveform used in pulse-width modulators

Note: this waveform is all positive

It can be lowered or raised using DC off set

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Common Waveforms-Triangle Waves

Off set triangle wave

This wave has equal positive and negative values

Off set equals Amplitude/2

Common Waveforms-Triangle Waves Voltage Measures

Peak-to-peak value 6.5 6 T Peak value

4 6 V A 3.46 2 6 V Peak value = peak- to-peak value 2 vv(t)

Amplitude Root Mean Square

0 (RMS) Value A 2  A RMS  2  3.5 3 0 2 4 6 8 10 12 14 16 0 t 16

Tim e A = peak amplitude value

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Measuring Waveform Amplitudes

An oscilloscope can measure A DVM can measure and all waveform amplitudes display RMS values and frequency

Use an oscilloscope to verify DVM frequency limits waveform generator outputs Use “True RMS” for non-sinusoids

Producing Electronic Waveforms

An instrument called a function generator produces all the waveforms covered in this presentation

Front Panel

Instrument Back

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End Lesson 16 EET 150 Coming Next: MORE WAVEFORM CHARACTERISTICS