Name: op-amp gain, feedback, and saturation
Uploaded: 2025-05-22T09:06:14.000Z
Duration: 1 min 17 s
Channel: JoVE

연산 증폭기의 등가 회로 모델을 고려하십시오. 출력 섹션은 출력 저항과 직렬로 연결된 전압 제어 소스로 구성됩니다.
입력 섹션에서 v1 및 v2는 각각 반전 및 비반전 단자에서 접지까지의 전압을 나타냅니다.
연산 증폭기의 출력 전압은 입력 전압 차이와 개방 루프 이득의 곱과 같습니다.
전압 차이가 작은 경우 연산 증폭기가 선형적으로 동작합니다. 전압이 전원 공급 장치 전압을 초과하면 연산 증폭기가 포화됩니다.
인가 전압과 네거티브 피드백의 조합은 연산 증폭기가 선형 범위 내에서 작동하도록 합니다.
최신 증폭기는 이득과 입력 저항이 커서 이상적인 연산 증폭기로 근사화할 수 있습니다.
이상적인 연산 증폭기는 무한 개방 루프 이득, 무한 입력 저항 및 0 출력 저항을 갖습니다. 입력 단자 전류와 입력 오프셋 전압은 모두 이상적인 연산 증폭기에서 0입니다.
또한 무한 대역폭을 가지고 있어 모든 주파수의 신호를 증폭할 수 있고 무한 슬루율을 가지고 있어 시간이 지남에 따라 출력 전압을 빠르게 변경할 수 있는 능력을 나타냅니다.

연산 증폭기의 특성.

일반적으로 연산 증폭기(op-amp)로 알려진 연산 증폭기는 특별히 설계된 전자 회로 부품입니다. 그 목적은 정의된 신호 처리 작업을 실행하기 위해 다른 회로 요소와 함께 작동하는 것입니다. Figure 1에 묘사된 연산 증폭기의 등가 회로 모델을 생각해 보십시오. 출력 섹션은 출력 저항 Ro와 병렬인 전압 제어 소스로 구성됩니다.

<img alt="Figure1" src="/files/ftp_upload/15077/15077_PT_Figure_1.svg" style="text-align: center; height: 166px;">
Figure 1: 비이상적 연산 증폭기의 등가 회로

Figure 1은 입력 저항 Ri가 입력 단자에서 관찰할 수 있는 Thėvenin 등가 저항과 동일하다는 것을 보여줍니다. 마찬가지로, 출력 저항 Ro 는 출력에서 ​​식별할 수 있는 Thėvenin 등가 저항에 해당합니다. 차동 입력 전압(vd)은 접지에 대한 비반전 단자의 전압과 접지에 대한 반전 단자의 전압 간의 차이로 계산됩니다.

연산 증폭기는 이 두 입력 간의 차이를 식별하고 이를 이득 A만큼 증폭하여 출력에 나타나는 전압을 생성합니다. 여기서 A는 개방 루프 전압 이득을 나타냅니다. 이는 출력에서 ​​입력으로의 외부 피드백이 없을 때 연산 증폭기의 이득을 나타내기 때문에 그렇게 명명되었습니다.

피드백은 연산 증폭기 회로를 연구할 때 이해해야 할 필수 개념입니다. 출력을 연산 증폭기의 반전 단자로 피드백하면 네거티브 피드백을 얻을 수 있습니다. 출력에서 입력까지의 피드백 경로가 존재하는 경우 출력 전압 대 입력 전압의 비율을 폐루프 이득이라고 합니다.

연산 증폭기에는 실질적인 한계가 있습니다. 그러한 제한 중 하나는 출력 전압의 크기가 |V_CC|를 초과할 수 없다는 것입니다. 기본적으로 전원 공급 장치 전압이 출력 전압을 결정하고 제한합니다. 차동 입력 전압에 따라 연산 증폭기는 포지티브 포화, 선형 영역 또는 네거티브 포화의 세 가지 모드 중 하나로 작동할 수 있습니다. vd 를 선형 범위 이상으로 높이려고 하면 연산 증폭기는 포화 상태에 도달하여 과정 = V_CC 또는 과정 = -V_CC 가 됩니다.

연산 증폭기의 등가 회로 모델을 고려하십시오. 출력 섹션은 출력과 직렬로 연결된 전압 제어 소스로 구성됩니다 ...

Education

교육

JoVE Core

Electrical Engineering

전기공학

Unit 1

제1단원

Operational Amplifiers

연산 증폭기

KEY TERMS AND CONCEPTS

주요 용어 및 개념

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 the noninverting terminal voltage and the inverting terminal voltage, both measured relative to ground. The op-amp compares these two input voltages and amplifies the difference by the gain A to produce an output voltage.

A is called the open-loop voltage gain because it describes the op-amp without feedback from the output back to the input. Feedback is important in op-amp circuits. Negative feedback is created by connecting the output to the inverting terminal. When that feedback path exists, the output-to-input ratio is the closed-loop gain.

Op-amps also have practical limits. Their output voltage cannot exceed the magnitude of the supply voltage, |VCC|. The power supply sets this limit. Depending on the differential input voltage, the op-amp can operate in positive saturation, the linear region, or negative saturation. If v d is pushed beyond the linear range, the output saturates at either v o = VCC or v o = -VCC.

Op-Amp Gain, Feedback, and Saturation

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...

characteristics of opamp

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...

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...

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

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 an op-amp compares input voltages, uses open-loop and closed-loop gain, and reaches positive or negative saturation when output limits are exceeded.

Op-Amp Gain, Feedback, and Saturation | 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, Feedback, and Saturation

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