Could someone please let me understand the term "Zero Drift" in an amplifier ?

[musthafafarhan]

Could someone please let me understand the term "Zero Drift" in an amplifier ?

I would like to know exactly what is zero drift and what it does in the sensing device. mainly, what advantages in it by using zero drift architecture amplifiers? :bang:

Thank you for your comments.

 

[chuckey]

Re: Could someone please let me understand the term "Zero Drift" in an amplifier ?

If you have a DC coupled amplifier, as the temperature changes, the leakage of current through devices will change. This causes the quiescent output voltage to wander about. The biggest problem area is the actual input , because any change of current here is amplified by the whole gain of the amplifier, while a bit of drift in the output stage would result in exactly that amount of DC shift at the output.
Negative feedback is used to reduced the drift. Careful balancing of amplifiers thermal performance and using differential amplifiers minimises the effect. This includes having very accurately matched source impedances for the inputs.
Frank
Frank

 

[crutschow]

Re: Could someone please let me understand the term "Zero Drift" in an amplifier ?

Input voltage offset drift can be a problem when measuring small DC voltages, so whether you need a "zero drift" amplifier or not depends upon how small a DC voltage you are measuring and the accuracy you need for that measurement.

If you do need the absolute minimum drift then you can use a zero offset (drift) amplifier which typically uses an AC chopper in an internal feedback loop in the amp to cancel any offset/drift.
Such an amplifier periodically compares the offset to 0V (common) and generates a correction voltage to keep the offset very near 0V (typically in the microvolt region).
The disadvantage of such a circuit is that it typically has a small output noise at the chopper frequency.

 

[FvM]

Re: Could someone please let me understand the term "Zero Drift" in an amplifier ?

You best proceed by studying architectures of "zero drift" amplifiers from major companies, e.g. ADI, TI, Linear, Maxim. Besides the common attribute of using a kind of chopper or auto-zero topology, there are large differences in terms of useful bandwidth, input characteristic and noise.