Lecture

Imperfections of Operational Amplifiers: Offset and Amplification Chain

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In course

EE-202: Electronics I

Les concepts de base permettant de comprendre, d'analyser et de concevoir les circuits à base d'AmpliOp, dédiés à l'acquisition et conditionnement des signaux analogiques sont traités en théorie et pratique. Cela englobe l'amplification, le filtrage, la co ...

Description

This lecture covers the imperfections of operational amplifiers (AO), focusing on offset voltage and amplification chain, polarization currents, and small signal frequency limitations. The instructor explains how imperfections manifest in real AOs, the dominance of the first gain stage's offset, and the impact of input impedance and bias currents. The lecture also delves into minimizing errors using resistors, the model of feedback amplifiers, and the bandwidth limitations of real AOs, including the concept of gain-bandwidth product. Additionally, the discussion includes the slew rate limitation for large signals and the effects of finite current on internal capacitances. Practical examples and calculations are provided to enhance understanding.

Instructors (2)

Adil Koukab

Cédric Meinen

Teaching & PhD Courses Electrical systems and electronics I EE-295 The course has the aim to provide the fundamental knowledge and experiences to understand basic electrical systems. Electrical systems and electronics II EE-296 The basic concepts enabling to understand and analysis the electronic systems dedicated to signals acquisition and processing (e.g. biosensors, physiological signals, ECG) are addressed. This includes the acquisition, amplification and filtering. El

Official source

Ontological neighbourhood

Physics

Electromagnetism: Electrical networks

Related concepts (31)

Amplifier

An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It is a two-port electronic circuit that uses electric power from a power supply to increase the amplitude (magnitude of the voltage or current) of a signal applied to its input terminals, producing a proportionally greater amplitude signal at its output. The amount of amplification provided by an amplifier is measured by its gain: the ratio of output voltage, current, or power to input.

Instrumentation amplifier

An instrumentation amplifier (sometimes shorthanded as in-amp or InAmp) is a type of differential amplifier that has been outfitted with input buffer amplifiers, which eliminate the need for input impedance matching and thus make the amplifier particularly suitable for use in measurement and test equipment. Additional characteristics include very low DC offset, low drift, low noise, very high open-loop gain, very high common-mode rejection ratio, and very high input impedances.

Negative-feedback amplifier

A negative-feedback amplifier (or feedback amplifier) is an electronic amplifier that subtracts a fraction of its output from its input, so that negative feedback opposes the original signal. The applied negative feedback can improve its performance (gain stability, linearity, frequency response, step response) and reduces sensitivity to parameter variations due to manufacturing or environment. Because of these advantages, many amplifiers and control systems use negative feedback.

Input impedance

The input impedance of an electrical network is the measure of the opposition to current (impedance), both static (resistance) and dynamic (reactance), into a load network that is external to the electrical source network. The input admittance (the reciprocal of impedance) is a measure of the load network's propensity to draw current. The source network is the portion of the network that transmits power, and the load network is the portion of the network that consumes power.

Operational amplifier

An operational amplifier (often op amp or opamp) is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output. In this configuration, an op amp produces an output potential (relative to circuit ground) that is typically 100,000 times larger than the potential difference between its input terminals. The operational amplifier traces its origin and name to analog computers, where they were used to perform mathematical operations in linear, non-linear, and frequency-dependent circuits.

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