Question
I’m using this component [AD8610] in a PLL design with +12/-5V supply. Now I
seen that
it works fine (despite the specs) also with +12 and 0V.
I need some info about possible problems I’ll have using the component in
this way (the spec is min +5/-5V).
Can you help me about this?
Answer
Operational amplifiers do not have a ground terminal. They can be powered by a
dual supply, either symmetrical or asymmetrical, or by a single supply.
So, a supply voltage of +12/-5V is analogous to +17/0V or +8.5/-8.5V with
regards to the power supply operating range. Therefore, +12/-5V supply is
within the operating voltage range for the AD8610,.
The AD8610 is JFET input operation amplifier, which means it features no
rail-to-rail input. As the output is also not rail-to-rail please pay close
attention to the input and output voltage range specifications found in the
"Electrical specifications" section of the www.analog.com/AD8610 datasheet,
table 2 (Vs=+/-13V). For your reference I am attaching the screenshot below:
Please remember, that the specifications for the input voltage range and output
voltage range are listed as absolute voltages, but the headroom (2.25 to 2.5V)
to the rails for +/-13V needs to be preserved compared to +12/-5V.
In addition, the reference level is shifted from ground to the center of the
supply voltage span. So, for a supply voltage of +12V/-5V the reference level
is raised to +3.5V compared to 0V for a symmetrical dual supply, like +/-5V or
+/-13V.
For more details regarding the input voltage range, single-supply operation or
rail-to-rail issues also kindly refer to www.analog.com/MT-035 and
www.analog.com/MT-041.
