What does high-speed operational amplifier mean?

Definition of High-Speed ​​Operational Amplifier

In fast A/D and D/A converters and video amplifiers, the conversion rate SR of the integrated operational amplifier must be high and the unit gain bandwidth BWG must be large enough. General-purpose integrated operational amplifiers are not suitable for high-speed applications. This is why high-speed operational amplifiers are produced.

Selection of Integrated Operational Amplifiers
Integrated operational amplifiers are the most widely used devices in analog integrated circuits. In various systems composed of operational amplifiers, due to different application requirements, the performance requirements of operational amplifiers are also different.

In situations where there are no special requirements, try to use general-purpose integrated operational amplifiers, which can reduce costs and ensure supply. When multiple operational amplifiers are used in a system, try to use multi-op-amp integrated circuits, such as LM324, LF347, etc., which are integrated circuits that package four operational amplifiers together.

To evaluate the performance of an integrated operational amplifier, we should look at its comprehensive performance. The merit factor K is generally used to measure the quality of an integrated operational amplifier, which is defined as: 

In the formula, SR is the conversion rate, the unit is V/ms, the larger the value, the better the AC characteristics of the op amp; Iib is the input bias current of the op amp, the unit is nA; VOS is the input offset voltage, the unit is mV. The smaller the Iib and VOS values ​​are, the better the DC characteristics of the op amp are. Therefore, for circuits that amplify AC signals such as audio and video, it is more appropriate to choose an op amp with a large SR (conversion rate); for circuits that process weak DC signals, it is more appropriate to choose an op amp with relatively high precision (i.e., the offset current, offset voltage and temperature drift are relatively small).

When selecting an integrated operational amplifier, in addition to the figure of merit, other factors should also be considered. For example, the nature of the signal source, whether it is a voltage source or a current source; the nature of the load, whether the output voltage and current of the integrated operational amplifier meet the requirements; environmental conditions, whether the integrated operational amplifier's allowable operating range, operating voltage range, power consumption and volume meet the requirements.

Characteristics of high-speed operational amplifiers
High-speed operational amplifiers are characterized by high conversion rate and wide frequency response. Common operational amplifiers include LM318, mA715, etc., with SR=50~70V/ms and BWG＞20MHz.

High-speed operational amplifiers are used
in fast A/D and D/A converters and video amplifiers, which require that the conversion rate SR of the integrated operational amplifier must be high and the unit gain bandwidth BWG must be large enough.