Decompensated Op Amp

Unity Gain Stable Op Amp

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OPAX607

SBOS981B – OCTOBER 2019 – REVISED FEBRUARY 2020

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Feature Description (continued)

8.3.4 Decompensated Architecture With Wide Gain-Bandwidth Product

Amplifiers such as the OPAX607 that are not unity-gain stable are referred to as decompensated amplifiers. The

decompensated architecture typically allows for higher GBW, higher slew rate, and lower noise compared to a

unity-gain stable amplifier with similar quiescent current. The increased available bandwidth reduces the rise time

and the settling time of the op amp, allowing for sampling at faster rates in an ADC-based signal chain.

compensation in a decompensated amp such as the OPAX607 increases the bandwidth for the same amount of

power. That is, the decompensated op amp has an increased bandwidth to power ratio when compared to a

unity-gain stable op amp of equivalent architecture. Besides the advantages in the above mentioned parameters,

an increased slew rate and a better distortion (HD2 and HD3) value is achieved because of the higher available

loop-gain, compared to its unity-gain counterpart. The most important factor to be considered is to ensure the op

called the rate of closure method. See the precision lab training videos from TI for a better understanding on

stability and for different techniques of ensuring stability.

Figure 2. Gain vs Frequency Characteristics for a Unity-Gain Stable Op Amp

and a Decompensated Op Amp

The OPAX607 is stable in a noise gain of 6 V/V (15.56 dB) or higher in conventional gain circuits; see Figure 3.

The device has 9 MHz of small-signal bandwidth (SSBW) in this gain configuration with approximately 65° of

phase margin. The high GBW and low voltage noise of the OPAX607 make the device suitable for general-

purpose, high-gain applications.