Name: op-amp adders and subtractors
Uploaded: 2024-04-11T12:48:35.000Z
Duration: 1 min 22 s
Channel: JoVE

加法放大器，或称加法器，利用运算放大器将多个输入信号合并为单一输出信号。
相反，差分放大器或减法器会放大两个输入信号之间的差值。
考虑一个带有运算放大器的音频混音电路。
当音频信号输入到输入通道时，输入电阻会产生流经反馈电阻的电流，从而产生输出电压。
根据基尔霍夫电流定律和欧姆定律，在运算放大器的输入节点处，输出电压与输入信号的加权和成正比。
一个基本的差分运算放大器电路可以在此混合信号中部分降低音频轨道噪声。
在反相节点和同相节点应用基尔霍夫电流定律（KCL）可得到两个方程。当两个节点电压相等时，即可推导出输出电压的表达式。
只有当电阻比满足特定条件时，差分放大器才能消除两个输入端共有的信号，从而获得差分输出。
当电阻 R2 等于 R1，且 R3 等于 R4 时，差分放大器起到减法器的作用。

和与差运算放大器

Sum and Difference OpAmps

运算放大器 (op-amps) 是一种多功能器件，其功能不仅仅限于放大。在这种情况下，需要对两种特定的运算放大器配置进行探讨：求和放大器和差分放大器。 加法放大器或加法器能够利用运算放大器将多个输入信号合并为单个输出信号。当音频信号被引入到其输入通道时，那么输入电阻器就会产生流过反馈电阻器的电流，从而产生输出电压。应用基尔霍夫电流定律和欧姆定律，能够得出输出电压成为输入信号的加权和。这种基本的差分运算放大器使得电路在减轻音频混音器应用中的音轨噪声方面发挥着重要作用。 <img alt="Equation1" src="/files/ftp_upload/15079/15079_PT_Equation_1.svg" style="text-align: center; height: 32px;"> 相反，差分放大器（通常称为减法器）能够放大两个输入信号之间的差异。通过在反相和同相节点的位置应用基尔霍夫电流定律来建立出两个方程。当两个节点上存在相同的电压时，便能够推导出其输出电压的表达式。然而，差分放大器必须满足特定的电阻比条件，以此来消除输入之间的公共信号。当相应支路中的电阻相等时，那么差分放大器便会起到减法器的作用。 <img alt="Equation2" src="/files/ftp_upload/15079/15079_PT_Equation_2.svg" style="text-align: center; height: 32px;"> 总之，运算放大器能够提供放大以及执行加法和减法任务的能力。加法放大器将其中的输入组合成加权和。差分放大器能够放大两个输入之间的差异并抑制其中的公共信号。从而为了解这些配置为信号处理和电路设计中的许多实际应用打开了大门。

求和放大器，或称加法器，利用运算放大器将多个输入信号合并为单一输出信号。  
相反，差分放大器……

Education

教育

JoVE Core

Electrical Engineering

电气工程

Unit 1

第一单元

Operational Amplifiers

运算放大器

KEY TERMS AND CONCEPTS

关键术语与概念

op-amp adders and subtractors

Operational amplifiers can be wired to add or subtract signals. In these two op-amp setups, the summing amplifier combines several input signals into one output, while the difference amplifier compares two inputs and amplifies their difference.

A summing amplifier is also called an adder. Input signals, such as audio signals, enter through input resistors. These resistors send currents through the feedback resistor, which produces an output voltage. Using Kirchhoff's current law and Ohm's Law, the output becomes a weighted sum of the inputs. This type of circuit can help reduce noise in audio mixer applications.

A difference amplifier is also called a subtractor. It amplifies the difference between two input signals. To describe its behavior, two equations are written by applying Kirchhoff's current law at the inverting and non-inverting nodes. When equal voltages appear across both nodes, an output voltage expression can be derived. Specific resistance ratios must be met for the circuit to cancel signals that are common to both inputs. When the resistances in the matching branches are equal, the difference amplifier works as a subtractor.

These op-amp circuits show that operational amplifiers do more than boost signals. They can perform addition and subtraction in circuit design. The summing amplifier creates a weighted total of multiple inputs, and the difference amplifier rejects common signals while highlighting the difference between two inputs. These ideas are useful in signal processing and many practical electronics applications.

Op-Amp Adders and Subtractors

operational amplifiers

Operational Amplifier Pinout and Signal Use

An operational amplifier, or op-amp, is a flexible circuit building block used in many electronic designs. It can act like a voltage-controlled voltage source, and it can also be used to create a voltage- or current-controlled current source. When resistors and capacitors are connected to its terminals, an op-amp can perform mathematical operations on signals. Op-amps are able to sum signals, amplify a signal, integrate it, or differentiate it. These features make them useful in practical...

design example: vintage mixing console

Op-Amp Preamp for a Vintage Console

A sound engineer designs an op-amp pre-amplifier for a vintage mixing console. The console’s output is too low for modern recording equipment, so the signal must be boosted before it can be used. The goal is to build a preamp that raises the audio level without changing the console’s character. The design must meet three clear requirements. It needs a gain of 10, an input impedance above 10 kilo-ohms so the console is not overloaded, and a frequency range that covers the full audio spectrum...

characteristics of opamp

Op-Amp Gain, Feedback, and Saturation

An operational amplifier, or op-amp, is an electronic circuit component used with other circuit parts to carry out a signal-processing task. It is often described with an equivalent circuit model. In that model, the output section includes a voltage-controlled source in parallel with the output resistance, R o. The model also shows the input resistance, R i, which is the Thevenin equivalent resistance seen at the input terminals. The differential input voltage, v d, is the difference between...

inverting and non-inverting opamps

Op-Amp Gain: Inverting, Noninverting, Buffer

Operational amplifiers can be used as inverting, noninverting, and buffer amplifiers. In these circuits, the output voltage depends on the input voltage and the resistor setup around the op-amp. In an inverting amplifier, the input voltage is sent through a resistor to the inverting terminal. The non-inverting terminal is grounded, and a feedback resistor links the inverting terminal to the output. Using Kirchhoff's Current Law and an ideal op-amp model, the gain can be found. This circuit...

sum and difference opamps

Operational amplifiers can be wired to add or subtract signals. In these two op-amp setups, the summing amplifier combines several input signals into one output, while the difference amplifier compares two inputs and amplifies their difference. A summing amplifier is also called an adder. Input signals, such as audio signals, enter through input resistors. These resistors send currents through the feedback resistor, which produces an output voltage. Using Kirchhoff's current law and Ohm's Law,...

characteristics of practical op amps

Op Amp Noise Rejection and Buffering

Practical op amps are used to separate useful signals from unwanted noise. A difference amplifier should ideally amplify only the difference between two input signals. In real circuits, though, the output depends on both differential gain and common-mode gain. The common-mode rejection ratio, or CMRR, measures how well an op amp rejects common-mode signals. Common-mode signals are the same on both inputs. A higher CMRR helps an op amp ignore noise and amplify the wanted signal, such as music...

integrator and differentiator

Op-Amp Circuits in Cruise Control

Op-amp circuits are used in cruise control systems to help cars keep a constant speed. In these systems, operational amplifiers, or op-amps, can work as integrators and differentiators. Both circuits use resistors and capacitors, which makes them compact and cost-effective. An integrator circuit produces an output that is proportional to the integral of the input signal. It is made by replacing the feedback resistor in a standard inverting amplifier with a capacitor. The output and input...

cascaded op amps

Op Amp Stages in Series

Operational amplifiers can be connected in series as separate stages. This cascade works because op-amps have very high input resistance and very low output resistance. Those properties help each stage keep its input-output relationship while driving the next stage. In a cascaded op-amp circuit, the output of one stage becomes the input of the next. Each stage adds gain to the signal as it passes through. The overall gain is the product of the gain of each stage. This design can improve...

instrumentation amplifier

ECG Signal Amplifier Design

An ECG signal amplifier helps an electrocardiography machine measure the heart’s electrical activity. ECG electrodes detect tiny voltage changes on the skin that come from depolarization of the heart muscle during each heartbeat. These signals are in the microvolt range, so they can be easily hidden by noise or interference. To solve this problem, ECG machines use an instrumentation amplifier. This amplifier boosts the ECG waveform while reducing common-mode noise, which is interference that...

key terms and concepts

Learn how op-amp adders and subtractors combine signals, compare two inputs, and use resistor ratios to create weighted sums and signal rejection.

Op-Amp Adders and Subtractors | 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

Op-Amp Adders and Subtractors

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