Circuitos Eletronicos Cap 01

7/27/2019 Circuitos Eletronicos Cap 01

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Introduo

REF:Sedra & Smith; M icroelectronic C


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Sinais

O rdio AM utiliza a imagem eltrica de uma fonte de sommodular a amplitude de uma onda portadora (carrier wave). Na do receptor, no processo de deteco, esta imagem separad

portadora e torna-se novamente som por meio de um autofalante

Rdio AM


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Figure 1.1 Two alternative representations of a signal source: (a) the Thvenin form, and (b) the Norton form.


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Figure 1.3 Sine-wave voltage signal of amplitude Va

and frequencyf = 1/T Hz. The angular frequency v= 2frad/s.

Sinais Peridicos


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0 0 0 0

4 1 1 1( ) 3 5 7 ..

3 5 7

Vv t senw t sen w t sen w t sen w t

Figure 1.4 A symmetrical square-wave signal of amplitude V.


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Figure 1.5 The frequency spectrum (also known as the line spectrum) of the periodic square wave of Fig. 1.4.


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Tempo & Frequncia

Srie de Fourier


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( ) ( )

1( ) ( )

2

j t

j t

F f t e dt

f t F e d

( )sV

Figure 1.2 An arbitrary voltage signal vs(t).

TransformadadeFourier

Sinais no Peridicos


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Figure 1.6 The frequency spectrum of an arbitrary waveform such as that in Fig. 1.2.


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Figure 1.7 Sampling the continuous-time analog signal in (a) results in the discrete-time signal in (b).

Sinais Discretos


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Figure 1.8 Variation of a particular binary digital signal with time.

Sinais Digitais


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Figure 1.9 Block-diagram representation of the analog-to-digital converter (ADC).


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Amplificadores de Sinais

Amplificador: elemento bsico em circuitos analgicos.

Inversor lgico: elemento bsico em circuitos digitais.

Necessidade: transdutores fornecem sinais fracos, na escala dou A, e com baixa energia.

Amplificador linear: sinal de sada possui mesma forma do sinal entrada, contendo as mesmas informaes com um mnimo de d


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0 ( ) ( )iv t Av t

Figure 1.11 (a) A voltage amplifier fed with a signal vI(t) and connected to a load resistanceRL. (b) Transfer characteristic of a linear vo

with voltage gainAv.


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Figure 1.12 An amplifier that requires two dc supplies (shown as batteries) for operation.


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EXEMPLO 1.1

Considere um amplificador operando a partir de fontes de

alimentao de 10V. Uma tenso senoidal de 1V de pico

est acoplada na entrada e uma tenso senoidal de 9V

de pico fornecida na sada, a uma carga de 1K. Oamplificador drena uma corrente de 9,5 mA de cada uma

das fontes de alimentao. A corrente de entrada do

amplificador senoidal, tendo 0,1 mA de pico. Calcule o

ganho de tenso, o ganho de corrente, o ganho de

potncia, a potncia drenada da fonte CC, a potncia

dissipada no amplificador e a eficincia.


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MAXIv

MAX

Iv

0MAXv

Figure 1.13a An amplifier transfer characteristic that is linear except for output saturation.

0MAXv

Caracterstica Sada x Entrada


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Figure 1.13b An amplifier transfer characteristic that is linear except for output saturation.


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Figure 1.14 (a) An amplifier transfer characteristic that shows considerable nonlinearity. (b) To obtain linear operation the amplifier is b

and the signal amplitude is kept small. Observe that this amplifier is operated from a single power supply, VDD.


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Figure 1.16 Symbol convention employed throughout the book.

Conveno de Notao


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Modelos de Circuitos para Amplificadores

Amplificador de Tenso


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010

1

1

v

in

out

A

R M

R K

0100

100

1

v

in

out

A

R K

R K

01

10

10

v

in

out

A

R K

R

EXEMPLO 1.3

Um amplificador composto de trs estgios em cascata. O amplificador

excitado por uma fonte de sinal com uma renitncia de sada de 100K.

carga na sada do amplificador de 100. Determine o ganho de tenso tota

o ganho de corrente e o ganho de potncia.


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Soluo

010

1

1

v

in

out

A

R M

R K

0100

100

1

v

in

out

A

R K

R K

01

10

10

v

in

out

A

R K

R


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Table 1.1 The Four Amplifier Types

Modelos de Circuitos para Amplificadores

Amplificador de Tenso Amplificador de Corrente

Amplificador deTranscondutncia

Amplificador deTransresistncia


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Exemplo: Ganho de Tenso


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Figure E1.20

Exemplo: Impedncia de Entrada


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Figure 1.20 Measuring the frequency response of a linear amplifier. At the test frequency v, the amplifier gain is characterized by its mag

and phasef.

Resposta em Freqncia dos Amplificadores

Pode-se caracterizar o desempenho de um amplificador etermos de sua resposta a entradas senoidais de diferentefrequncias.

Vo/ Vimagnitude do ganho do ana frequncia de teste

f fase do ganho do amplificadona frequncia de teste

Largura de Banda


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Largura deBanda

Largura de banda (bandwidth): faixa de valores na qual o ganamplificador praticamente constante, limitado a um decrscimo de

Deve-se projetar o amplificador de modo que sua largura de band

maior ou igual a largura de banda do espectro dos sinais que dser amplificados.

3dB


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Figure 1.22 Two examples of STC networks: (a) a low-pass network and (b) a high-pass network.

Circuitos Passa Baixas e Passa Altas


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Figure 1.23 (a) Magnitude and (b) phase response of STC networks of the low-pass type.

Diagrama deBode


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Figure 1.24 (a) Magnitude and (b) phase response of STC networks of the high-pass type.


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Figure 1.25 Circuit for Example 1.5.

Exemplo: Determine a Resposta em Frequncia...


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Figure 1.26 Frequency response for(a) a capacitively coupled amplifier, (b) a direct-coupled amplifier, and (c) a tuned or bandpass amp


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Figure 1.27 Use of a capacitor to couple amplifier stages.

Inversor Lgico Digital


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Figure 1.29 Voltage transfer characteristic of an inverter. The VTC is approximated by three straightline segments. Note the four param

(VOH, VOL, VIL, and VIH) and their use in determining the noise margins (NMHandNML).

NMH Margem de rudo para o nvel alt

NML Margem de rudo para o nvel ba

Inversor Lgico Digital


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Figure 1.30 The VTC of an ideal inverter.


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Figure 1.31 (a) The simplest implementation of a logic inverter using a voltage-controlled switch; (b) equivalent circuit when vIis low;

equivalent circuit when vIis high. Note that the switch is assumed to close when vIis high.


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Figure 1.32 A more elaborate implementation of the logic inverter utilizing two complementary switches. This is the basis of the CMOS

in Section 4.10.


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Figure 1.33 Another inverter implementation utilizing a double-throw switch to steer the constant currentIEE toRC1 (when vIis high) or

low). This is the basis of the emitter-coupled logic (ECL) studied in Chapters 7 and 11.


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Figure 1.34 Example 1.6: (a) The inverter circuit after the switch opens (i.e., fort 0). (b) Waveforms ofvIand vO. Observe that the sw

to operate instantaneously. vO rises exponentially, starting at VOL and heading toward VOH.


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Figure 1.35 Definitions of propagation delays and transition times of the logic inverter.

Exerccios Propostos


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Figure P1.58

Exerccios Propostos


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Figure P1.63


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Figure P1.65


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Figure P1.67


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Figure P1.68


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Figure P1.72


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Figure P1.77


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Figure P1.79

Circuitos Eletronicos Cap 01

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