What is the Common mode voltage range of ADA4522-2 ?

Hi Ashok,

Rail to rail output amplifier means that output of the amplifier can go almost equal to the supply rails (of course there will be few millivolts drops to the Vce or Vds of the output transistor). But this is not necessarily mean that this kind of amplifier is also a rail to rail input.

It is useful in achieving the maximum output signal swing with low supply voltage which results in increase of dynamic range.

Rail to rail input, on the other hand, means that the input can span the entire supply voltage range.

You can easily check it on the spec table and look for the input voltage range.

This is for the ADA4522:You can see that the input voltage needs 1.5V headroom from the positive supply rail.

This is for the AD8638: it need 2V headroom from the supply rail. This is also the reason why you only see 3V on the spice model.

Since your circuit is a buffer and your input voltage can reach up to the same level as your positive supply rail, then you may need an amplifier that is rail to rail input and rail to rail output. .

Now there are amplifiers that are both rail to rail input and rail to rail output like the ADA4091, ADA4084, etc.

But for the zero drift amplifier portfolio which are well known for ultra low offset and drift, only the ADA4528 is  rail to rail input and rail to rail output amplifier but it can only go supply voltage of up to 5.5V.

There are also  only 3 Zero Drift amplifier that can accommodate supply voltage of =>+/-5V but there are not rail to rail input.

What is your target accuracy specs in terms of offset and drift?

Also what is your minimum input voltage?

Are you expecting negative input voltage?

Because if not, then you can probably use the ADA4528 with V+ tied to 5V and V- tied to ground.

I hope this helps.

Best regards,

Emman

Hi Ashok,

Rail to rail output amplifier means that output of the amplifier can go almost equal to the supply rails (of course there will be few millivolts drops to the Vce or Vds of the output transistor). But this is not necessarily mean that this kind of amplifier is also a rail to rail input.

It is useful in achieving the maximum output signal swing with low supply voltage which results in increase of dynamic range.

Rail to rail input, on the other hand, means that the input can span the entire supply voltage range.

You can easily check it on the spec table and look for the input voltage range.

This is for the ADA4522:You can see that the input voltage needs 1.5V headroom from the positive supply rail.

This is for the AD8638: it need 2V headroom from the supply rail. This is also the reason why you only see 3V on the spice model.

Since your circuit is a buffer and your input voltage can reach up to the same level as your positive supply rail, then you may need an amplifier that is rail to rail input and rail to rail output. .

Now there are amplifiers that are both rail to rail input and rail to rail output like the ADA4091, ADA4084, etc.

But for the zero drift amplifier portfolio which are well known for ultra low offset and drift, only the ADA4528 is  rail to rail input and rail to rail output amplifier but it can only go supply voltage of up to 5.5V.

There are also  only 3 Zero Drift amplifier that can accommodate supply voltage of =>+/-5V but there are not rail to rail input.

What is your target accuracy specs in terms of offset and drift?

Also what is your minimum input voltage?

Are you expecting negative input voltage?

Because if not, then you can probably use the ADA4528 with V+ tied to 5V and V- tied to ground.

I hope this helps.

Best regards,

Emman