Abstract

De-compensated op amps have improved noise, slew rate, harmonic distortion, etc., but external compensation is required for stable operation. This article shows how to compensate such amplifiers and realize the performance enhancement it provides in a unity-gain configuration.

The THS4011 and THS4021 operational amplifiers are used to illustrate the superior performance of a de-compensated op amp. These are voltage-feedback op amps that use the same basic amplifier structure. The THS4011 is internally compensated to be stable at unity gain, whereas the THS4021 has its internal compensation relaxed so that external compensation is required.

Introduction

When I was writing this article, I was talking about it with a colleague of mine and his first response was, "What do you mean by 'de-compensated'? I know what an uncompensated op amp is, but I never heard of a de-compensated op amp." With that in mind I will start by explaining what I mean by a de-compensated amplifier.

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