Name: ecg signal amplifier design
Uploaded: 2025-07-11T07:24:08.000Z
Duration: 1 min 25 s
Channel: JoVE

在心电图机中，电极可检测每次心跳时心肌去极化引起的皮肤微小电变化。
这些微伏级信号可能会被噪声或干扰所淹没。
为纠正这一问题，心电图机采用仪器放大器来放大心电信号波形，同时最大限度地减少共模噪声信号。
仪器放大器是一种差分放大器，包含六个电阻、三个端子，以及一个连接在增益设置端子之间的外部电阻。
它能放大输入信号之间的微小差异，同时抑制两个输入共有的信号。
输出电压是电压增益与输入电压差的乘积。通过仅调节外部电阻，即可轻松调整增益。
仪器放大器具有高输入阻抗、低输出阻抗、高增益稳定性和高共模抑制比。
高输入阻抗可通过避免信号负载来防止信号失真，而高共模抑制比（CMRR）有助于抑制电极导线拾取的噪声，例如来自其他设备的电干扰。
仪器放大器被用于生物医学仪器和通信领域。

仪表放大器

心电图 (ECG) 机是用来监测心脏中电活动的重要医疗设备。它的工作原理是检测每次心跳期间由于心肌去极化而导致皮肤上产生了微小的电变化。然而，这些信号在微伏的范围之内，从而导致其很容易被噪声或干扰所掩蔽。 为了能够克服这一挑战，心电图机使用了仪表放大器。这种专用放大器旨在放大心电图波形，同时最大限度地减少共模噪声信号所产生的影响，例如来自其他设备的电气干扰。 仪表放大器是差分放大器中的一种。其电路中包括六个电阻器、三个端子以及连接在增益端子之间的外部电阻器。该放大器的功能是放大输入信号之间的微小差异，同时抑制两个输入共有的信号。 放大器的输出电压是由电压增益和输入电压差的乘积来进行决定。通过改变外部电阻器的值可以轻松的调整其增益，从而能够对放大的过程提供其相应的灵活性和控制。 仪表放大器具有几个关键的特性，这非常适合用于心电图机。因为它们具有高输入阻抗、低输出阻抗、高增益稳定性和高共模抑制比 (CMRR)。 高输入阻抗通过避免信号负载来防止信号失真，并以此来确保来自心脏中电信号的完整性。较高的CMRR能够使放大器有效的抑制电极引线所拾取的噪声，例如来自其他设备的电气干扰，从而来提高心电图波形的质量。 除了在心电图机中的应用之外，由于仪表放大器具有其独特的特性，因此会将其广泛的应用在各种生物医学仪器和电信领域。

在心电图机中，电极可检测到皮肤上因每次心肌去极化而产生的微小电变化……

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

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 appears on both inputs. It works as a difference amplifier, so it strengthens the small voltage difference between the two input signals and rejects the signals they share.

The circuit uses six resistors, three terminals, and an external resistor connected between the gain set terminals. The output voltage depends on the voltage gain and the input voltage difference. The gain can be adjusted by changing the value of the external resistor, which gives the circuit flexibility.

Instrumentation amplifiers are well suited for ECG systems because they have high input impedance, low output impedance, high gain stability, and a high common mode rejection ratio, or CMRR. High input impedance helps prevent signal loading, so the heart signal is not distorted. High CMRR helps block interference picked up by the electrode leads, such as noise from other equipment, and improves the ECG waveform. These amplifiers are also used in other biomedical instrumentation and telecommunication applications.

ECG Signal Amplifier Design

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

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

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 instrumentation amplifier helps an ECG machine boost tiny heart signals, reject noise, and improve waveform quality using adjustable gain and high CMRR.

ECG Signal Amplifier Design | 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

ECG Signal Amplifier Design

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