Name: reading frequency response on bode plots
Uploaded: 2024-07-08T13:20:02.000Z
Duration: 1 min 26 s
Channel: JoVE

Considere uma unidade de eletrocardiograma que utiliza um filtro passa-baixa com uma função de rede complexa representada por sua magnitude e ângulo de fase.
O ganho logarítmico de decibéis é calculado multiplicando o logaritmo de base dez da magnitude da função de rede por 20.
Os gráficos de Bode são gráficos semilogarítmicos que exibem o ganho logarítmico em decibéis e o ângulo de fase em graus entre as frequências.
Em frequências mais baixas, o ganho logarítmico e o ângulo de fase se aproximam de zero.
Isso resulta em linhas horizontais no gráfico de Bode, conhecidas como assíntotas de baixa frequência.
Em frequências mais altas, os cálculos de ganho e ângulo de fase refletem sua dependência da frequência.
Eles são descritos como linhas retas com inclinações negativas e são conhecidos como assíntotas de alta frequência.
As assíntotas de baixa e alta frequência se cruzam em um canto, também conhecido como frequência de canto.
Nessa frequência, a magnitude assintótica se desvia em quase -3 decibéis do valor exato e o ângulo de fase é de aproximadamente -45 graus.
Os gráficos de bode assintóticos são boas aproximações dos gráficos de bode reais.

gráficos de bode

Os gráficos de Bode são ferramentas gráficas que usam escalas logarítmicas para frequência no eixo -x e ganho em decibéis no eixo- y. Este método logarítmico permite que uma ampla faixa de frequências seja exibida de forma compacta, permitindo a análise dos efeitos dos componentes no comportamento do circuito em um amplo espectro de frequências.
Uma função de rede representa a relação entre a saída e a entrada de um sistema, com a magnitude e o ângulo de fase derivados da função de rede complexa. O ganho logarítmico em decibéis é determinado multiplicando o logaritmo de base dez da magnitude da função de rede por 20. O ganho em um gráfico de Bode é expresso logaritmicamente. A unidade de ganho logarítmico é o decibel, também conhecido como ganho em dB. Decibéis (dB) quantificam o ganho, onde 1 dB é um décimo de bel, o que homenageia Alexander Graham Bell.
Os gráficos de Bode, que são gráficos semi logarítmicos, mostram o ganho logarítmico em decibéis e o ângulo de fase em graus em uma faixa de frequências. Esses gráficos facilitam a compreensão da resposta de frequência de um sistema.
Em frequências mais baixas, tanto o ganho logarítmico quanto o ângulo de fase se aproximam de zero, formando linhas horizontais no gráfico de Bode conhecidas como assíntotas de baixa frequência. Estas linhas indicam um impacto mínimo do filtro nos sinais nessas frequências. À medida que a frequência aumenta, os cálculos do ganho e do ângulo de fase refletem sua dependência da frequência. No gráfico de Bode, essas dependências aparecem como linhas retas com inclinações negativas, chamadas assíntotas de alta frequência. Estas linhas demonstram como o filtro atenua sinais de frequência mais alta. As assíntotas de baixa e alta frequência se cruzam na frequência de canto. Aqui, a magnitude assintótica desvia cerca de -3 decibéis do valor exato, marcando uma mudança significativa na resposta do filtro. Além disso, o ângulo de fase na frequência de canto é de aproximadamente -45 graus.
Os gráficos de Bode assintóticos fornecem aproximações razoáveis ​​dos gráficos de Bode reais, permitindo uma análise simplificada, mantendo uma precisão razoável.

Gráficos de Bode

Considere uma unidade de eletrocardiograma que utiliza um filtro passa-baixa com uma função de rede complexa representada por sua magnitude e ângulo de fase.
O...

Education

JoVE Core

Electrical Engineering

Engenharia Elétrica

Unit 1

Unidade 1

Frequency Response

Resposta de Frequência

KEY TERMS AND CONCEPTS

TERMOS E CONCEITOS-CHAVE

Bode Plots

reading frequency response on bode plots

Bode plots show how a circuit or system responds across frequency. They use a logarithmic frequency scale on the x-axis and gain in decibels on the y-axis. This format makes it easier to display a wide range of frequencies and to see how circuit parts affect behavior over that range.

A network function gives the ratio of output to input for a system. Its complex form provides both magnitude and phase angle. The logarithmic gain on a Bode plot comes from the magnitude, calculated by multiplying the base-ten logarithm of that magnitude by 20. The gain is measured in decibels, or dB. A decibel is one-tenth of a bel, and the unit honors Alexander Graham Bell.

Because Bode plots are semilogarithmic graphs, they show gain in dB and phase angle in degrees over frequency. This makes the frequency response of a system easier to study. At low frequencies, both gain and phase angle approach zero. These flat regions are called low-frequency asymptotes, and they show that the filter has little effect on the signal there.

As frequency rises, the gain and phase angle change with frequency. On the plot, this appears as straight lines with negative slopes called high-frequency asymptotes. These lines show that the filter attenuates higher-frequency signals. The low- and high-frequency asymptotes meet at the corner frequency. At that point, the asymptotic magnitude is about -3 decibels from the exact value, and the phase angle is about -45 degrees. Asymptotic Bode plots give a reasonable approximation of the actual plot and make analysis simpler while keeping useful accuracy.

Reading Frequency Response on Bode Plots

analyzing-filter-response-with-bode-plots

network function of a circuit

How Transfer Functions Shape Circuit Response

Transfer functions show how a circuit responds as signal frequency changes. They describe the link between input and output in frequency response analysis. This makes them useful for studying how circuits behave in electronics and engineering. A transfer function is a mathematical tool that relates phasor output to phasor input. It can be written as voltage gain, current gain, transfer impedance, or transfer admittance. The poles and zeros are the most important parts of the function. Zeros...

frequency response of a circuit

Inductive Circuit Frequency Response

Inductive circuit frequency response shows how a circuit with an inductor reacts to different frequencies. The analysis starts in the time domain and then moves into the frequency domain. In that step, the inductor is replaced by an impedance, and the circuit is written with phasors, which are sinusoidal signals shown with magnitude and phase. The transfer function describes how the output changes compared with the input at each frequency. A key parameter is the time constant, which is the...

gain

Circuit Gain and Phase Shift

Circuit gain and phase shift describe how a linear circuit changes a sinusoidal input voltage or current. These properties matter in circuits with reactive elements, because the response depends on the input frequency. As the frequency changes, the gain and phase shift also change. Gain compares the size of the output sinusoid to the size of the input sinusoid. If Vin is the input and Vout is the output, the gain K is the ratio of the output amplitude to the input amplitude. A gain greater...

bode plots

Bode plots show how a circuit or system responds across frequency. They use a logarithmic frequency scale on the x-axis and gain in decibels on the y-axis. This format makes it easier to display a wide range of frequencies and to see how circuit parts affect behavior over that range. A network function gives the ratio of output to input for a system. Its complex form provides both magnitude and phase angle. The logarithmic gain on a Bode plot comes from the magnitude, calculated by multiplying...

transfer function and bode plots-i

Transfer Function Gain and Origin Effects

Transfer function gain and poles or zeros at the origin shape a system's Bode plot. The transfer function is often written in standard form after the polynomial coefficients are normalized. In that form, the constant gain, zeros, poles, and quadratic terms all appear clearly. The poles and zeros mark critical frequencies where the output magnitude and phase change noticeably. The constant gain K creates a fixed magnitude and phase term. Its magnitude is 20 log 10 K in decibels, and its phase...

transfer function and bode plots-ii

Bode Plot Slope and Phase Changes

Bode plots show how a transfer function changes with frequency. The standard form includes constant gain, poles and zeros at the origin, simple poles and zeros, and quadratic poles and zeros. Each part shapes the system response in a different way. A simple zero sets the magnitude trend first. The Bode magnitude plot stays flat at low frequencies, near 0 dB, and then rises at 20 dB per decade after the corner or break frequency, ω1. That corner frequency is where the straight-line...

bode plots construction

Reading Frequency Response with Bode Plots

Bode plots show the frequency response of a system with a magnitude plot and a phase plot. Both plots use a logarithmic frequency axis. In control system analysis, this makes it easier to see how a transfer function changes with frequency. To build a Bode plot, start with the transfer function H(ω). After normalization, the function includes constant gain, zeros, and poles. Each term affects the plot in a different way. A constant gain of 10 gives a starting magnitude of 20 dB, since 20...

series resonance

Series Resonance in RLC Circuits

Series resonance in an RLC circuit happens when the inductive reactance and capacitive reactance are equal. An RLC circuit contains a resistor, an inductor, and a capacitor. The impedance of the circuit is the ratio of the supply voltage to the circuit current. At resonance, the imaginary part of the impedance becomes zero. The frequency at which this occurs is called the resonant frequency. It depends on the inductance (L) and capacitance (C) of the circuit. Mathematically, the resonant...

characteristics of series resonant circuit

characteristics-of-series-resonant-circuit

Series Resonance and RLC Filter Behavior

Series resonance in an RLC circuit happens when the inductor, capacitor, and resistor are connected in series. At the resonant frequency, the inductive reactance and capacitive reactance are equal in size but opposite in sign, so they cancel each other. As a result, the circuit impedance becomes very small and is mainly set by the resistance. The resonant frequency of a series RLC circuit can be calculated from its inductance and capacitance. At this frequency, the current reaches its maximum...

parallel resonance

Parallel RLC Tuning at Resonance

A parallel RLC circuit uses a resistor, inductor, and capacitor connected to the same nodes. Because they share the same voltage, the circuit is analyzed with admittance, which describes how easily current can flow. In a parallel RLC circuit, admittance helps show how the circuit responds as the frequency changes. Resonance happens when the net reactance is zero. At that point, the capacitive and inductive effects cancel each other out. The resonant frequency is found from this condition. At...

frequency response of op amp circuits

Op Amp Gain and Bode Plot Basics

Operational amplifiers are used for signal conditioning, filtering, and mathematical tasks such as addition, subtraction, integration, and differentiation. Their frequency response shows how amplifier gain changes as the input frequency changes. This makes the gain of an op-amp a key idea in circuit design. At low frequencies, an op-amp can hold a constant gain called the dc gain, A0. As frequency rises, the gain starts to drop after the corner frequency, or break frequency, ω1. In other...

passive filters

Audio Frequency Control with Passive Filters

Passive filters shape the frequency spectrum of electrical signals. They use only passive parts such as resistors, inductors, and capacitors. Because they do not need an external power source, they can let selected frequency ranges pass or block others in many applications. Low-pass filters pass signals below the cutoff frequency, ωc, and reduce signals above it. In audio systems, they can send bass frequencies to woofers or subwoofers. For an RC low-pass filter, the transfer function H(s)...

active filters

Active Filter Design and Frequency Response

Active filters use op-amps, resistors, and capacitors to shape a signal's frequency response. They remove unwanted frequency components while keeping the parts of the signal that are needed. The design depends on the choice of resistor and capacitor values, which set the cutoff points and help define the overall response. A first-order low-pass active filter passes signals below a cutoff frequency and reduces signals above it. Its transfer function includes the low-frequency gain, also called...

scaling

Circuit Component Scaling for Filters

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design example

Touch-Tone Filter Design Example

Touch-tone telephony uses dual-tone multi-frequency (DTMF) signaling and a filter design example to show how keypad tones are separated. It replaced the old rotary dial with a matrix-style keypad arranged in four rows and three columns. Each of the 12 buttons produces a unique signal pair. Every key press creates two sinusoidal tones at the same time. One tone comes from a low-frequency group between 697 and 941 Hz. The other comes from a high-frequency group between 1209 and 1477 Hz. This...

key terms and concepts

Learn how Bode plots use decibels, phase angle, and asymptotes to show frequency response, including corner frequency and filter behavior.

Reading Frequency Response on Bode Plots | JoVE K12

JoVE Core Electrical Engineering offers easy-to-understand animated videos that cover fundamental concepts of electric circuits along with circuit analysis techniques. It incorporates first-order and second-order circuits using operational amplifiers and circuit transformation concepts. The inclusion of practical design examples and real-world applications through scientist-in-action videos adds significant educational value, making complex concepts accessible.

electrical engineering

Reading Frequency Response on Bode Plots

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