Zero drift Op amps

[golfnut]

There is a benefit to keeping the DC offsets minimal in the dc coupled stage of these detectors to minmise masking of small signals .

In the absence of Air Cal dc offset removal HW and SW - has anybody tried the Zero drift op amps

linear tech, Ti, analog, etc do them.

Input offsets can be
Maximum offset Voltage 5µV

So ideal beyond ac coupled stages - for filters leading into to comparator.

S

[Davor]

IMHO they are a waste of good money and expectations. Say, what do you do with a non-motion detector when you start searching? Press a little button to null it? You'd do the very same thing with those zero drift babies.

[golfnut]

Are you saying they need to be reset by the user? I cant find that in datasheets - i will re read.


I thought a limiting factor on detector sens is the dc offsets in the DC coupled stages of the det.


In use a lot of detectors prompt for Air Balance - which is the DC offset removal of which I speak.
Common in zero If Rx as your aware. (Gsm phones do this before each Rx slot - to maximise sens)

Then GND bal as usual. (Two control loops, zeroed at the start, then automatically zeroed by the machine in use n times/sec)


If in the IGSL or IDX, the opamp preceeding the comparator had little or no input dc offset, then its output dc level would be lower.

The comparator could then 'see' smaller targets - which previously would have been beneath the relatively large dc offset and therefore undetectable or invisible.

Typical zero drift opamp



S

[Davor]

IGSL, IDX, and all other motion compensated rigs do not have a problem of DC offset because it influences only their sensitivity setup, and it is not critical at all. Places where DC offset is critical are with non-motion rigs where offset is carefully maintained. But even with these rigs the residual offset that is laser trimmed and drift compensated in these speciality op amps is not of utmost importance because you'll compensate manually more often for other reasons than the op amp drift. You may use these op amps for sure, but you'll hardly ever going to notice any advantage.