Name: analyzing an op amp audio filter
Uploaded: 2024-04-11T12:48:50.000Z
Duration: 1 min 18 s
Channel: JoVE

Em um sistema de áudio, o circuito de filtro processa o sinal de áudio amplificado de um amplificador, atenuando fortemente os componentes do sinal com baixas frequências.
Considere o circuito de filtro mais simples que consiste em um amplificador operacional em uma configuração inversora acoplado aos resistores R1 e R2 e ao capacitor C1. Qual é o sinal de saída resultante para um sinal de entrada conhecido?
A impedância do capacitor é calculada usando a frequência angular derivada da expressão no domínio do tempo para a tensão de entrada.
O circuito equivalente no domínio da frequência representa o sinal de entrada na forma polar e as impedâncias Z1 e Z2. A impedância Z2 corresponde à combinação paralela do capacitor C1 e do resistor R2.
Aplicando a lei atual de Kirchoff e a lei de Ohm no nó produz uma equação nodal para um amplificador operacional ideal. Esta equação, quando reorganizada, indica que a relação entre a saída e a tensão de entrada é igual à razão negativa das impedâncias.
Ao substituir os valores conhecidos e calculados nesta equação, a tensão de saída é determinada na forma polar, que é então convertida no domínio do tempo.

circuitos ac amplificadores operacionais

Dentro de um sistema de áudio, o circuito de filtro desempenha um papel fundamental no processamento do sinal de áudio amplificado de um amplificador. Sua função principal é atenuar significativamente os componentes do sinal com frequências mais baixas, moldando assim a saída de áudio. As operações deste circuito são examinadas, com foco na configuração fundamental do filtro. Esta configuração envolve um amplificador operacional disposto em uma configuração inversora acoplada a resistores (R1 e R2) e um capacitor (C1).

<img alt="Figure1" src="/files/ftp_upload/15116/15116_PT_Figure_1.svg" style="text-align: center; height: 164px;" />

Quando confrontado com um sinal de entrada conhecido, o desafio reside na determinação do sinal de saída resultante. A primeira etapa envolve o cálculo da impedância do capacitor, que é obtido empregando a frequência angular derivada da expressão no domínio do tempo da tensão de entrada.

<img alt="Equation1" src="/files/ftp_upload/15116/15116_PT_Equation_1.svg" style="text-align: center; height: 36px;" />

Como resultado, a análise transita para o domínio da frequência, onde o sinal de entrada é representado na forma polar juntamente com os componentes de impedância Z1 e Z2. Z2 refere-se explicitamente à combinação paralela do capacitor C1 e do resistor R2. O núcleo da análise baseia-se na aplicação da Lei dos Nós de Kirchhoff e da lei de Ohm em um nó específico do circuito, formulando assim uma equação nodal para um amplificador operacional ideal. Esta equação, quando reorganizada, revela uma visão crítica: a relação entre a tensão de saída e a tensão de entrada é inversamente proporcional à razão das impedâncias.

<img alt="Equation2" src="/files/ftp_upload/15116/15116_PT_Equation_2.svg" style="text-align: center; height: 36px;" />

Os valores conhecidos e calculados são habilmente substituídos nesta equação para revelar a tensão de saída na forma polar. O resultado, representando a tensão de saída, pode então ser transformado no domínio do tempo, proporcionando uma compreensão abrangente da resposta do circuito de filtro ao sinal de entrada. Para a análise, muitas vezes são assumidas propriedades ideais do amplificador operacional, incluindo o princípio de que nenhuma corrente entra em nenhum de seus terminais de entrada e que a tensão em seus terminais de entrada permanece zero.

Circuitos AC Amplificadores Operacionais

Em um sistema de áudio, o circuito de filtro processa o sinal de áudio amplificado de um amplificador, atenuando fortemente os componentes do sinal com baixa ...

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Electrical Engineering

Engenharia Elétrica

Unit 1

Unidade 1

AC Circuit Analysis

Análise de Circuitos CA

KEY TERMS AND CONCEPTS

TERMOS E CONCEITOS-CHAVE

Op Amp AC Circuits

analyzing an op amp audio filter

An op amp audio filter shapes an amplified sound signal by strongly reducing the lower-frequency parts. In this circuit, the focus is on a basic filter setup used after an amplifier in an audio system. The filter uses an operational amplifier in an inverting arrangement with resistors R1 and R2 and a capacitor C1.

The analysis starts with a known input signal and asks for the output signal. To solve it, the capacitor impedance is found first. That requires the angular frequency from the time-domain form of the input voltage, so the work moves into the frequency domain.

In the frequency domain, the input signal is written in polar form. The impedances Z1 and Z2 are then used, with Z2 representing the parallel combination of capacitor C1 and resistor R2. At the same time, the ideal op amp assumptions are used. No current enters either input terminal, and the voltage across the input terminals is zero.

The final step is applying Kirchhoff's current law and Ohm's law at one node in the circuit. This creates a nodal equation for the ideal op amp. When that equation is rearranged, the output-to-input voltage ratio is shown to be inversely proportional to the impedance ratio. The known values are then substituted to find the output voltage in polar form, and that result can be converted back to the time domain for a full description of the filter response.

Analyzing an Op Amp Audio Filter

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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

Analyzing an Op Amp Audio Filter

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