S
Stephen Boulet
Guest
I was wondering, what are the downsides to using a dual-supply op amp in
a single-supply configuration?
Stephen
a single-supply configuration?
Stephen
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Bob Monsen
Guest
Stephen Boulet wrote:
ground. 'normal' opamps often can't get near the power rails, so using
them near ground doesn't work out so well.
However, if you are using a rail-to-rail opamp, it should be ok.
---
Regards,
Bob Monsen
Single supply opamps are designed so input and output can be nearI was wondering, what are the downsides to using a dual-supply op amp in
a single-supply configuration?
Stephen
ground. 'normal' opamps often can't get near the power rails, so using
them near ground doesn't work out so well.
However, if you are using a rail-to-rail opamp, it should be ok.
---
Regards,
Bob Monsen
M
Michael Black
Guest
Stephen Boulet (stephen_at@nospam.theboulets.net) writes:
off a single supply, they are biased to the half way point, so
in effect they do see a dual supply. Run it off a 12v supply,
and bias it to 6volts, and the opamp sees 6volts on the positive
supply line and -6volts on the negative supply line, relative to
that bias point. This isn't any different from running the opamp
off a -6/+6 power supply, since the opamp will have 12 volts across
it.
One disadvantage of running an op-amp off a single supply is
that the input and output will not be at ground, but at half of
the supply voltage (as a result of the biasing). So there won't
be zero DC volts on those lines (unless you measure in reference
to the bias point), and so DC coupling may be out of the question
depending on applications.
The real thing is that "single supply op-amps" are designed so
the output can go closer to the supply voltage. This is useful
since if you're running it off a single supply, usually that is
a lower voltage than the sum when you've got a bipolar power supply,
12volts versus 24volts. The greater headroom of the "single supply
op-amps" means they work better at those lower voltages.
Michael
Really there's no such thing as a single supply op-amp. If they runI was wondering, what are the downsides to using a dual-supply op amp in
a single-supply configuration?
Stephen
off a single supply, they are biased to the half way point, so
in effect they do see a dual supply. Run it off a 12v supply,
and bias it to 6volts, and the opamp sees 6volts on the positive
supply line and -6volts on the negative supply line, relative to
that bias point. This isn't any different from running the opamp
off a -6/+6 power supply, since the opamp will have 12 volts across
it.
One disadvantage of running an op-amp off a single supply is
that the input and output will not be at ground, but at half of
the supply voltage (as a result of the biasing). So there won't
be zero DC volts on those lines (unless you measure in reference
to the bias point), and so DC coupling may be out of the question
depending on applications.
The real thing is that "single supply op-amps" are designed so
the output can go closer to the supply voltage. This is useful
since if you're running it off a single supply, usually that is
a lower voltage than the sum when you've got a bipolar power supply,
12volts versus 24volts. The greater headroom of the "single supply
op-amps" means they work better at those lower voltages.
Michael
J
James Meyer
Guest
On 24 May 2005 06:32:14 GMT, et472@FreeNet.Carleton.CA (Michael Black) wroth:
biased if they have input and output voltages that are not outside the rail
voltages. They can be biased, but it is not because that's the only way to make
them work.
Jim
That last statement is wrong. Single-supply opamps do not need to beStephen Boulet (stephen_at@nospam.theboulets.net) writes:
I was wondering, what are the downsides to using a dual-supply op amp in
a single-supply configuration?
Really there's no such thing as a single supply op-amp. If they run
off a single supply, they are biased to the half way point, so
in effect they do see a dual supply.
biased if they have input and output voltages that are not outside the rail
voltages. They can be biased, but it is not because that's the only way to make
them work.
Jim
P
Pooh Bear
Guest
Stephen Boulet wrote:
Graham
Depends what you're doing with it. There may be no downside at all.I was wondering, what are the downsides to using a dual-supply op amp in
a single-supply configuration?
Graham