6 Detailed Description

6.1 Overview

The OPA134 series are ultra-low distortion, low-noise operational amplifiers fully specified for audio applications.

A true FET input stage is incorporated to provide unmatched sound quality and speed for exceptional audio

performance. This, in combination with high output drive capability and excellent DC performance, allows for use

in a wide variety of demanding applications. In addition, the OPA134 has a wide output swing, to within 1V of the

rails, allowing increased headroom and making this op amp an excellent choice for any audio circuit.

6.2 Feature Description

6.2.1 Total Harmonic Distortion

The OPAx134 series of operational amplifiers have excellent distortion characteristics. THD+Noise is below

0.0004% throughout the audio frequency range, 20Hz to 20kHz, with a 2kΩ load. In addition, distortion remains

relatively flat through the wide output voltage swing range, providing increased headroom compared to other

audio amplifiers, including the OP176/275.

Headroom is a subjective measurement, and can be thought of as the maximum output amplitude allowed while

still maintaining a low level of distortion. In an attempt to quantify headroom, TI defines very low distortion as

0.01%. Headroom is expressed as a ratio which compares the maximum allowable output voltage level to a

standard output level (1mW into 600Ω, or 0.7746Vrms). Therefore, OPA134 series of operational amplifiers,

which have a maximum allowable output voltage level of 11.7Vrms (THD+Noise < 0.01%), have a headroom

specification of 23.6dBu. See Figure 5-4.

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OPA134, OPA2134, OPA4134

SBOS058B – DECEMBER 1997 – REVISED NOVEMBER 2024

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Product Folder Links: OPA134 OPA2134 OPA4134