Name: op-amp gain: inverting, noninverting, buffer
Uploaded: 2024-04-11T12:48:35.000Z
Duration: 1 min 20 s
Channel: JoVE

反相放大器通过一个电阻将输入电压连接到反相输入端，将同相输入端接地，并在反相输入端与输出端之间连接一个反馈电阻。
通过应用基尔霍夫电流定律（KCL）并假设运算放大器为理想状态，可确定增益的表达式。
反相放大器在放大输入信号的同时会反转其极性，因此可用于噪声消除。
麦克风选择输入的噪声信号，并在消噪电路中将该信号反相，以消除噪声。
反相运算放大器在音频处理中具有信号放大、转换和滤波的应用。
同相放大器将输入电压直接施加到同相端，在反相端与地之间连接一个电阻，并使用一个电阻实现负反馈。
在反相输入端应用基尔霍夫电流定律（KCL），并代入电压值，可得到电压增益的表达式。
如果反馈电阻被短路或输入电阻处于开路状态，则增益变为1，从而形成一个电压跟随器。
它们将高阻抗输入转换为低阻抗输出，从而实现向低阻抗负载的高效信号传输。

反相和同相运算放大器

Inverting and Non-inverting OpAmps

在反相放大器中，输入电压能够通过电阻器连接到反相端子。同时其中的同相端接地，反相端和输出端之间建立起反馈电阻，如图1所示。 <img alt="Figure1" src="/files/ftp_upload/15078/15078_PT_Figure_1.svg" style="text-align: center; height: 176px;"> 图1：反相放大器 其目的是辨别输入电压 (vi) 和输出电压 (vo) 之间的关系。在应用基尔霍夫电流定律 (KCL) 的同时假设其运算放大器是理想的，则可以得出其中的增益表达式。反相放大器能够在放大输入信号的同时反转其输入信号的极性。值得注意的是，增益仅取决于连接到运算放大器的外部元件，增益的值则为反馈电阻除以输入电阻所得出的值。 运算放大器的另一个关键应用场景是同相放大器，如图2所示。 <img alt="Figure2" src="/files/ftp_upload/15078/15078_PT_Figure_2.svg" style="text-align: center; height: 172px;"> 图2：同相放大器 在这里，输入电压 (vi) 能够直接的施加在同相输入端，而电阻器R则能够连接在地和反相端之间。这里的重点是输出电压和电压增益。在反相端应用KCL并代入电压值即可得到电压增益的表达式。如果反馈电阻发生短路或输入电阻产生开路，那么其增益就会变为单位增益，从而形成电压跟随器或单位增益放大器。由于这种电路具有高输入阻抗，因此能够使其用作中间级（或缓冲）放大器来将一个电路与另一个电路进行隔离。

反相放大器通过一个电阻将输入电压连接到反相输入端，将同相输入端接地，并具有一个反馈……

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 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 reverses the polarity of the input signal while also amplifying it. The gain depends on the external resistors, and it is the feedback resistance divided by the input resistance.

A noninverting amplifier works differently. The input voltage is applied directly to the non-inverting terminal. A resistor is placed between the ground and the inverting terminal, and the feedback path helps determine the output voltage and voltage gain. Applying Kirchhoff's Current Law at the inverting terminal gives the gain expression.

If the feedback resistor is short-circuited or the input resistor is open-circuited, the gain becomes unity. This creates a voltage follower, also called a unity gain amplifier. Because it has high input impedance, this type of circuit is useful as a buffer that separates one circuit from another.

Op-Amp Gain: Inverting, Noninverting, Buffer

op-amp-gain-inverting-noninverting-buffer

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

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

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,...

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 inverting and noninverting op-amps set voltage gain, reverse signal polarity, and form a unity-gain buffer with high input impedance.

Op-Amp Gain: Inverting, Noninverting, Buffer | 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 Gain: Inverting, Noninverting, Buffer

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