AD8662: Supply voltage

Document created by analog-archivist Employee on Feb 23, 2016
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Our customer wants to use AD8662 with +/-5V supply voltage.
Datasheet mentions 16V supply voltage range.
Can you confirm that it is OK to supply +/-5V for this device ?
Are there some cases with AD amplifiers where it is not possible ?

 

The AD8662 will work correctly with supplies of any value between 5V and 16V.
This information is on the front page of the AD8662 data sheet, but I am afraid
that some op-amps are not so clear, nor is the difference between single and
dual supplies for op-amps spelled out on their data sheets as it ought to be.

Many op-amps list the range of supply voltages in the data tables which are
found just after the front page(s). You will see the note on pages 4 & 6 of the
AD8662 in the PSRR section
                       "Vs = 5 V to 16 V"

Sometimes, but not on the AD8662 data sheet, the "POWER SUPPLY"
section of this part of the data sheet lists the limits.

But you can also look in the graphs which follow the data tables.
Several different graphs may indicate the correct operating range, but on the
AD8662 data sheet Fig 20 clearly shows supply current v supply voltage. You can
see the current rises abruptly at around
4 V, which suggests that the device starts to function correctly here. The
current does not then change very much from 5 to 16 V, which again suggests
that operation does not vary much with supply in this range.

No monolithic op-amp designed since 1967 of which I am aware has a third
"ground" supply pin - the have two, Vdd (V+) and Vss (V-).
There is therefore no difference, from the amplifier's point of view, between a
single +V supply and a ±V/2 supply. (There will be very important differences
in the signal ground references, but we are not discussing these here.)

So for any op-amp with supply range X (min) to Y (max) the supply may be a
single supply with a value between X and Y, or a dual supply with values of ±X/
2 to ±Y/2, or a dual supply with unequal positive or negative values as long as
the TOTAL supply to the op-amp lies in the range X to Y. In all of these cases
it is very important to define the signal ground correctly.

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