Input voltage noise or Input offset voltage?

What the parameter in the data sheet of a op-amp tell us minimum detectable voltage in case of non inverting type configuration?
Input voltage noise or Input offset voltage?

I think the sum of both noise and offset, because they're an AC signal onto a DC offset.

padiyar said:

What the parameter in the data sheet of a op-amp tell us minimum detectable voltage in case of non inverting type configuration?
Input voltage noise or Input offset voltage?

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Minimum detectable ac or dc voltage?

noise strongly depends on bandwidth, offset - not. Therefore answer will depend on additonal conditions of spec

LvW said:

Minimum detectable ac or dc voltage?

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It is ac voltage from high frequency PZT for medical ultrasound

Offset should be irrelevant for a suitable designed AC amplifier. Amplifier noise and signal-to-noise ratio (SNR) achievable in a particular application depends on various parameters. Of course device voltage and current noise density in the frequency range of interest, but also source impedance, circuit dimensioning and the effective application signal bandwidth. Minimum detectable voltage isn't a usual term in amplifier design, but you can define a similar quantity based on a SNR specification.

padiyar,
here is a real world example:

A sampled data system requires that there are no signal components above the frequency determined by the Nyquist limit.
For this reason, a band limiting lowpass (anti-aliasing filter) is used prior to sampling.
However, no real lowpass can perform an ideal signal attenuation for frequencies far above the "cut-off"-frequency (that means: in fact there is no real "cut-off").
But, fortunately, there is always a noise floor - and it is sufficient to require a damping in the lowpass stop band just below the noise level.

FvM said:

Offset should be irrelevant for a suitable designed AC amplifier. Amplifier noise and signal-to-noise ratio (SNR) achievable in a particular application depends on various parameters. Of course device voltage and current noise density in the frequency range of interest, but also source impedance, circuit dimensioning and the effective application signal bandwidth. Minimum detectable voltage isn't a usual term in amplifier design, but you can define a similar quantity based on a SNR specification.

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According to your view if two opamp have similar voltage and current noise density with the both opamp subjected to same gain of 40db one having offset voltage of 250uV and another having 5mV will amplify a small voltage of 500uV in the similar way?

both(...)will amplify a small voltage of 500uV in the similar way?

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Quite right. You should select the OP for minimal noise (or other AC parameters) essential in your application. By the way, an input amplifier with a single ended input stage will show better noise performance than the differential OP input stage, assuming equal transistor noise parameters. Thus for lowest noise, you should go for a discrete amplifier design or a specialized monolithic LNA.