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High speed, high voltage amplifier for cap. load

J

[email protected]

I'd like to drive a ~400pF load ("electrode" below) at 1-10MHz,
100Vpkpk. I had a previous posting about this, and I got some
excellent advice about doing this with a RF amplifier (50 Ohm out,
which I have) + transformer (for voltage step-up) + resonator (for Z
matching to 50 Ohm):

.. ____________
.. G n1:n2 ,-----+------------+---+--)___________}---|
.. __|\__ T | | | | coax electrode (400pF)
.. | |/ | || # # _|_ | 1pF __
.. Vac # || # # L C --- '-||--)__ coax carries RF
.. |______| || # # | voltage-monitor
.. gapless | | Cdc | sig to cap. divider
.. pot core '--+--+---||--(#)--+-- gnd
.. | \ \
.. | gapped current transformer
.. dc bias --\/\/--' pot core or small sense resistor

I'd like to know if it's possible to just drive this 400pF load with an
op-amp or common-emmitter amp. instead (so that I don't have to
impedence match). For example, I've seen the APEX amps, but those
can't quite reach 10MHz (good solution for 1 MHz though). I'd like to
be able to do the following:

__|\____ electrode (400pF to ground)
| |/
Vac
|
gnd

and be able to vary Vac from 1-10MHz with the amplifier putting out
100Vpp across the electrode. No coax necessary here. Am I dreaming
when I'm basically asking for a 10MHz 100Vpp op-amp?
 
W

Winfield Hill

[email protected] wrote...
I'd like to drive a ~400pF load ("electrode" below) at 1-10MHz,
100Vpkpk. I had a previous posting about this, and I got some
excellent advice about doing this with a RF amplifier (50 Ohm out,
which I have) + transformer (for voltage step-up) + resonator (for
Z matching to 50 Ohm):

. ____________
. G n1:n2 ,-----+------------+---+--)___________}---|
. __|\__ T | | | | coax electrode (400pF)
. | |/ | || # # _|_ | 1pF __
. Vac # || # # L C --- '-||--)__ coax carries RF
. |______| || # # | voltage-monitor
. gapless | | Cdc | sig to cap. divider
. pot core '--+--+---||--(#)--+-- gnd
. | \ \
. | gapped current transformer
. dc bias --\/\/--' pot core or small sense resistor
Click to expand...


Yes, I recognize my ASCII-circuit drawing. You're welcome.
I'd like to know if it's possible to just drive this 400pF load
with an op-amp or common-emmitter amp. instead (so that I don't
have to impedence match). For example, I've seen the APEX amps,
but those can't quite reach 10MHz (good solution for 1 MHz though).
I'd like to be able to do the following:

__|\____ electrode (400pF to ground)
| |/
Vac
|
gnd

and be able to vary Vac from 1-10MHz with the amplifier putting
out 100Vpp across the electrode. No coax necessary here.
Click to expand...

No coax? How are you going to transport the 100V 10MHz signal?
Also, how do you arrive at 400pF, that's a lot for an electrode,
which would make one think some coax was involved, at 30pF/foot.
Am I dreaming when I'm basically asking for a 10MHz 100Vpp op-amp?
Click to expand...

OK, the slew rate of a 100V sine-wave signal would be S = dV/dt
= 2pi f V, where V is the peak voltage of 50V, so S = 3200V/us.
The current required by your capacitor would be i = C dV/dt = C S
= 1.25A. For this sine wave you'd need a wideband amplifier that
could deliver 1.25A peak and 50V peak, with a slew rate exceeding
3200V/us. I know such a beast, ah, amplifier, could be built, but
I've never seen one.

If your 1 to 10MHz signal is not a sine wave, for example if it's
a SWIFT waveform with components extending up to 10MHz, you need
to know the maximum amplitude of the near-10MHz components. Then
you can calculate a new lower Imax and slower required slew rate.
Perhaps the amplifier you really need may be a bit more practical.
 
J

Joerg

Hello,

What kinds of signals to you want to deliver? Pulses? Continuous wave?
Can it be square waves?

Regards, Joerg
 
J

[email protected]

Hi Win. I put up some pics of the linear trap at

http://www.stanford.edu/~jwodin/lineartrap/

in case you were interested. Also, a CAD picture of the vacuum system
is at

http://www.stanford.edu/~jwodin/lineartrap/vacuumsystem.jpg

where the long dimension is ~ 3ft, just to get an idea.
No coax? How are you going to transport the 100V 10MHz signal?
Also, how do you arrive at 400pF, that's a lot for an electrode,
which would make one think some coax was involved, at 30pF/foot.
Click to expand...

So, we're going to wire the electrodes like this, in cross section:


-- --
+-----------|E1| |E2|-----+
| -- -- |
| Vdc(i) (no RF)
| +--------------+
| |
Vac+Vdc(i) -- --
| |E3| |E4|
| -- --
| |
+---------------------

each pair of jumpered electrodes in the picture is ~25pF to ground, and
there are 16, which gives a total of 400pF. The 4 electrodes in this
cross section have the same DC voltage (Vdc(i)), but each set of 4 will
have a different DC voltage. All pairs E1+E4 will have 1MHz, 100Vpp.
For running at 1MHz, I was thinking

+-----------------+
| A1 | C1
| _______|\_____|____||_______|E1+E4
| | |/ || | |
| Vac | (Set 1)
| | | +---|E2+E3
| Gnd | | |
| R1 | |
| Vdc(1)-+--vvvv----------+ |
| | |
| |__________________|
|
| C1
|______________________||_______|E1+E4
| || | |
| R1 | (Set 2)
| Vdc(2)----vvvv----------+
| |
.. |______________________|E2+E3 .
.. | .
.. .
..
.. C1
|______________________||_______|E1+E4
|| | |
R1 | (Set 16)
Vdc(16)---vvvv----------+
|
|______________________|E2+E3
|



Where A1 is an APEX PA98 op-amp, C1>>25pF (DC blocking cap so that DC
doesn't get on RF supply), R1~1MOhm or higher, and Vdc(i) is one of
your DC supply circuits (they work great!). I was going to build this
all on a PCB board, which will be mounted next to our vacuum system.
The RF+DC lines will come out on some multi-conductor amphenol mil-spec
connectors that screw right onto our vacuum system feedthroughs (very
short distance, small parallel capacitance compared to the electrodes,
so negligible). Therefore, reflections shouldn't be a problem here.
Line to line capacitive pickup shouldn't be an issue, since
everything is at the same frequency.

Now here's the trick -- we wanted to be able to run this system
anywhere from 1-10MHz with not too much tuning. I didn't think that
I could get this kind of tuning range from the pot core set up that you
suggested earlier.

OK, the slew rate of a 100V sine-wave signal would be S = dV/dt
= 2pi f V, where V is the peak voltage of 50V, so S = 3200V/us.
The current required by your capacitor would be i = C dV/dt = C S
= 1.25A. For this sine wave you'd need a wideband amplifier that
could deliver 1.25A peak and 50V peak, with a slew rate exceeding
3200V/us. I know such a beast, ah, amplifier, could be built, but
I've never seen one.
Click to expand...

Yes, I agree that that sounds crazy. The APEX that you suggested
should work fine at 1MHz for us though.
If your 1 to 10MHz signal is not a sine wave, for example if it's
a SWIFT waveform with components extending up to 10MHz, you need
to know the maximum amplitude of the near-10MHz components. Then
you can calculate a new lower Imax and slower required slew rate.
Perhaps the amplifier you really need may be a bit more practical.
Click to expand...
I assume a SWIFT waveform just has harmonics at different frequencies?
I know groups who have trapped atoms (ions) in these traps with square
waves even, though they say the trap stability goes down. Perhaps the
best way to have tunability from 1-10MHz is still to go with your
transformer+resonator? If so, could you suggest a good place for some
pot cores? Of course, the dream was just to be able to dial in a
frequency and have it run there.
 
J

[email protected]

Hi Joerg, it's continuous. So, we'll be supplying a sine wave at say 1
MHz, and then at some point, would like to switch over to say 5 MHz,
without any sort of massing tuning or rewinding of transformers.
 
F

Frank Miles

Hi Win. I put up some pics of the linear trap at

http://www.stanford.edu/~jwodin/lineartrap/

in case you were interested. Also, a CAD picture of the vacuum system
is at

http://www.stanford.edu/~jwodin/lineartrap/vacuumsystem.jpg

where the long dimension is ~ 3ft, just to get an idea.
Click to expand...

[snip description]
Where A1 is an APEX PA98 op-amp, C1>>25pF (DC blocking cap so that DC
doesn't get on RF supply), R1~1MOhm or higher, and Vdc(i) is one of
your DC supply circuits (they work great!). I was going to build this
all on a PCB board, which will be mounted next to our vacuum system.
The RF+DC lines will come out on some multi-conductor amphenol mil-spec
connectors that screw right onto our vacuum system feedthroughs (very
short distance, small parallel capacitance compared to the electrodes,
so negligible). Therefore, reflections shouldn't be a problem here.
Line to line capacitive pickup shouldn't be an issue, since
everything is at the same frequency.

Now here's the trick -- we wanted to be able to run this system
anywhere from 1-10MHz with not too much tuning. I didn't think that
I could get this kind of tuning range from the pot core set up that you
suggested earlier.
Click to expand...

If you need something more broadband, perhaps you could use something
like a "T-coil" to couple the amplifier output to the capacitive load.
Done right, this should get you about a 2.7x reduction in drive current.
This was done, for example, in oscilloscope vertical amplifier outputs
(driving the capacitive deflection plates). The trade-off is that the Apex
amps want to see a capacitive load, and the T-coil inputs look resistive.

Yes, even with T-coils this would be monstrous, and really hard to achieve.
Would your arrangement be any more feasible if you split the amplifier
into pieces? Using separate amplifiers for each electrode set?
This might reduce current levels to where real physical transistors
might exist that could support these frequencies, currents, and voltages.
As it stands it looks pretty tough...
Yes, I agree that that sounds crazy. The APEX that you suggested
should work fine at 1MHz for us though.
I assume a SWIFT waveform just has harmonics at different frequencies?
I know groups who have trapped atoms (ions) in these traps with square
waves even, though they say the trap stability goes down. Perhaps the
best way to have tunability from 1-10MHz is still to go with your
transformer+resonator? If so, could you suggest a good place for some
pot cores? Of course, the dream was just to be able to dial in a
frequency and have it run there.
Click to expand...

Even if you used sinusoids, switching resonanting inductors wouldn't be
easy, you would have to use a bunch of relays and the whole distributed
nature of the system would "add challenges".

Sounds like a fun project!

-frank
--
 
C

colin

I'd like to drive a ~400pF load ("electrode" below) at 1-10MHz,
100Vpkpk. I had a previous posting about this, and I got some
excellent advice about doing this with a RF amplifier (50 Ohm out,
which I have) + transformer (for voltage step-up) + resonator (for Z
matching to 50 Ohm):
Click to expand...

Have you looked at crt cathode drivers ?
they have the voltage and speed, not sure what their current is offhand,
400pf at 10mhz is 40 ohms; 100vpk pk = >1amp pk
you can get 3 in one package,
maybe have one per electrode ?
otherwise ive no idea how well they would work in parallel tho,

Colin =^.^=
 
J

Joerg

Hello,
Hi Joerg, it's continuous. So, we'll be supplying a sine wave at say 1
MHz, and then at some point, would like to switch over to say 5 MHz,
without any sort of massing tuning or rewinding of transformers.
Click to expand...

If you want that kind of luxury you will have no choice but to build a
linear amplifier with a whole lot of power. Look at video transistors
that drive the cathodes or gates of CRTs. Those are cheap. You'll need
lots of them. Driving 400pF up to 100Vpp at 10MHz is like a tractor
pulling contest. Old trucker wisdom: There is nothing that can replace
lots of cubic inches, except more cubic inches.

Oh, and make sure there is a large heat sink ;-)

Regards, Joerg
 
W

Winfield Hill

[email protected] wrote...
Hi Win. I put up some pics of the linear trap at
http://www.stanford.edu/~jwodin/lineartrap/ in case you were
interested. Also, a CAD picture of the vacuum system is at
http://www.stanford.edu/~jwodin/lineartrap/vacuumsystem.jpg
where the long dimension is ~ 3ft, just to get an idea.
Click to expand...

How does the trap and the vacuum system go together?
So, we're going to wire the electrodes like this, in cross section:

-- --
+-----------|E1| |E2|-----+
| -- -- |
| Vdc(i) (no RF)
| +--------------+
| |
Vac+Vdc(i) -- --
| |E3| |E4|
| -- --
| |
+---------------------

each pair of jumpered electrodes in the picture is ~25pF to ground,
and there are 16, which gives a total of 400pF. The 4 electrodes
in this cross section have the same DC voltage (Vdc(i)), but each
set of 4 will have a different DC voltage. All pairs E1+E4 will
have 1MHz, 100Vpp. For running at 1MHz, I was thinking

+-----------------+
| A1 | C1
| _______|\_____|____||_______|E1+E4
| | |/ || | |
| Vac | (Set 1)
| | | +---|E2+E3
| Gnd | | |
| R1 | |
| Vdc(1)-+--vvvv----------+ |
| | |
| |__________________|
|
| C1
|______________________||_______|E1+E4
| || | |
| R1 | (Set 2)
| Vdc(2)----vvvv----------+
| |
. |______________________|E2+E3 .
. | .
. .
.
. C1
|______________________||_______|E1+E4
|| | |
R1 | (Set 16)
Vdc(16)---vvvv----------+
|
|______________________|E2+E3
|

Where A1 is an APEX PA98 op-amp, C1>>25pF (DC blocking cap so that
DC doesn't get on RF supply), R1~1MOhm or higher, and Vdc(i) is one
of your DC supply circuits (they work great!). I was going to build
this all on a PCB board, which will be mounted next to our vacuum
system.
Click to expand...

I'm sorry Jesse, the APEX amps don't come close to handling your task.
The RF+DC lines will come out on some multi-conductor amphenol mil-spec
connectors that screw right onto our vacuum system feedthroughs (very
short distance, small parallel capacitance compared to the electrodes,
so negligible). Therefore, reflections shouldn't be a problem here.
Click to expand...

I'd like to know more detail about those connectors and feedthroughs.
Line to line capacitive pickup shouldn't be an issue, since
everything is at the same frequency.
Click to expand...

Yes, but you still want to shield those lines, transmitter/antenna
city, you know, otherwise. But I do have a suggestion.
Now here's the trick -- we wanted to be able to run this system
anywhere from 1-10MHz with not too much tuning. I didn't think that
I could get this kind of tuning range from the pot core set up that
you suggested earlier.
Click to expand...

That's correct.
Yes, I agree that that sounds crazy. The APEX that you suggested
should work fine at 1MHz for us though.
Click to expand...

At 1MHz, yes, but sorry, not to 10MHz. Have you examined the specs
with an eye to the required compensation, and how that slows down
the slew rate? And the limited GBW product, which kills operation
up to 10MHz. It appears the APEX amp is at least 4x short of your
goal, even if it was driving only one 25pF electrode.

But I do have a practical solution for you, which I'll describe in
my next post. Right now I'm going to walk the dog with my wife.
 
W

Winfield Hill

Winfield Hill wrote...
[email protected] wrote...

I'm sorry Jesse, the APEX amps don't come close to handling your
task (at up to 10MHz).

... but you still want to shield those lines, transmitter/antenna
city, you know, otherwise. But I do have a suggestion.


At 1MHz, yes, but sorry, not to 10MHz. ...
Click to expand...

OK, here's my practical solution. The first issue to consider
is that you'll find more high-performance amplifier ICs available
at low voltages (and high currents), because that's where you'll
find the manufacturability / customer-demand sweet spot. So the
first part of my solution is to use a step-up transformer. It's
easy to make 0.5 to 20MHz wideband transformers. Furthermore,
we can use its leakage-inductance property to help us at 10MHz.

Second, we go looking for candidate amplifiers, such as the Analog
Devices' AD815. This is a dual amp, good for 50Vpp into 50 ohms
in bridge mode (500mA) up to 20MHz (G=2). See figure 52 in the
datasheet, http://www.analog.com/en/prod/0,2877,AD815,00.html

If we assume 40Vpp, a transformer with a modest 1:2.5 turns ratio
would work well. We'll use this to drive two electrode pairs, say
70pF total including a short bit of coax. This capacitance would
look like 438pF on the primary, or j36 ohms at 10MHz, and require
550mA to drive at 10MHz. Aha, just at the limit for the AD815.

Each amplifier sees a 20Vpp swing, corresponding to a slew rate
of 630V/us at 10MHz, well under the AD815's 900V/us capability.

All transformers have leakage inductance, which limits their high-
frequency performance. But, if we design the leakage inductance
to resonate with the capacitive load near 10MHz, with L = 3.6uH,
we can reduce the loading effect of the capacitance, and thereby
reduce the increasing current requirement on the amplifier near
10MHz. If the leakage inductance is less than 3.6uH, we'll add
a small discrete inductor. We'll also have to add a resistor in
parallel with the transformer to damp the resonance, 330 ohms will
be about right. This looks like 53 ohms at the primary, and that
will be the amplifier's load at lower frequencies. The current
load may actually drop a bit near 10MHz, which is nice. This will
also help stabilize the amplifier, which would be unhappy driving
a purely-capacitive load.

.. | A1
.. |__________|\____ T1 ___________| E1+E4
.. | | |/ | # | | |
.. | inv #||# 330 | (Set 1)
.. | | A2 #||# 10W |
.. | |___|\____| #___|_______| E2+E3
.. | |/ | |
.. | AD815 | 1nF_|_
.. | dc1 -,-
.. | |___| E1+E4
.. | ac sig 100k | |
.. | bus ,--/\/--' (Set 2)
.. | |
.. | |___________| E2+E3
.. | | |
.. | dc2

You could build eight of these, each in its own little Pomona box,
mounted near its electrodes, to drive the entire linear trap. Or,
given the operation near the limit of the AD815, you could relax
the scene and make 16 of them... You could parallel amplifiers,
as shown in figure 50. Or you could make two sets in each box...

Fortunately the AD815 is cheap, under $10. I suggest the 15-Lead
through-hole SIP package, still available from Rochester, because
it's easier to heat sink (Pd = about 4 to 5 watts). The wideband
transformers will be small, inexpensive and easy to wind yourself.

Divide and conquer, eight or sixteen, that's my suggestion.
 
K

Ken Smith

I'd like to drive a ~400pF load ("electrode" below) at 1-10MHz,
100Vpkpk. I had a previous posting about this, and I got some
Click to expand...


Just a bit of ASCII art thinking out loud:



150V
!
!!-
-------!! N MOSFET
!!-
!
100V--->!----+
!
!!-
-------!! N MOSFET
!!-
!
50V--->!----+
!
!!-
-------!! N MOSFET
!!-
!
GND--->!----+
!
!!-
-------!! N MOSFET
!!-
!
-50V--->!----+
!
!!-
-------!! N MOSFET
!!-
!
-100V--->!----+
!
!!-
-------!! BIGGER N MOSFET
!!-
!
+------- Output
!
!!-
-------!! BIGGER P MOSFET
!!-
!
100V---!<----+
!

ETC


It has way too many parts in it but it drives a capacitive load with a lot
less loss than the simple linear amplifier. The drop across the
conducting transistors can always be about 50V.
 
W

Winfield Hill

john jardine wrote...
Winfield wrote ...
[clip interesting stuff]
Second, we go looking for candidate amplifiers, such as the Analog
Devices' AD815. This is a dual amp, good for 50Vpp into 50 ohms
in bridge mode (500mA) up to 20MHz (G=2). See figure 52 in the
datasheet, http://www.analog.com/en/prod/0,2877,AD815,00.html
Click to expand...

Dammit, my lip's bleeding :).
I've now looked at this datasheet twice and still can't get my
head around the spec's being quoted.
How does figure 15, page 5, of the datasheet fit into the grand
scheme of things?.
Click to expand...

None. That means for example that Vos changes by 4mV as the output
swings to 6V, which is less than 0.1%, and of little concern here.
If you were making a precision A/D amplifier, it might be an issue.
 
J

john jardine

Winfield Hill said:
Winfield Hill wrote... [clip interesting stuff]
Second, we go looking for candidate amplifiers, such as the Analog
Devices' AD815. This is a dual amp, good for 50Vpp into 50 ohms
in bridge mode (500mA) up to 20MHz (G=2). See figure 52 in the
datasheet, http://www.analog.com/en/prod/0,2877,AD815,00.html
Click to expand...

Dammit, my lip's bleeding :).
I've now looked at this datasheet twice and still can't get my head around
the spec's being quoted.
How does figure 15, page 5, of the datasheet fit into the grand scheme of
things?.
regards
john
 
C

colin

Winfield Hill said:
Winfield Hill wrote...

OK, here's my practical solution. The first issue to consider
is that you'll find more high-performance amplifier ICs available
at low voltages (and high currents), because that's where you'll
find the manufacturability / customer-demand sweet spot. So the
first part of my solution is to use a step-up transformer. It's
easy to make 0.5 to 20MHz wideband transformers. Furthermore,
we can use its leakage-inductance property to help us at 10MHz.

Second, we go looking for candidate amplifiers, such as the Analog
Devices' AD815. This is a dual amp, good for 50Vpp into 50 ohms
in bridge mode (500mA) up to 20MHz (G=2). See figure 52 in the
datasheet, http://www.analog.com/en/prod/0,2877,AD815,00.html

If we assume 40Vpp, a transformer with a modest 1:2.5 turns ratio
would work well. We'll use this to drive two electrode pairs, say
70pF total including a short bit of coax. This capacitance would
look like 438pF on the primary, or j36 ohms at 10MHz, and require
550mA to drive at 10MHz. Aha, just at the limit for the AD815.

Each amplifier sees a 20Vpp swing, corresponding to a slew rate
of 630V/us at 10MHz, well under the AD815's 900V/us capability.

All transformers have leakage inductance, which limits their high-
frequency performance. But, if we design the leakage inductance
to resonate with the capacitive load near 10MHz, with L = 3.6uH,
we can reduce the loading effect of the capacitance, and thereby
reduce the increasing current requirement on the amplifier near
10MHz. If the leakage inductance is less than 3.6uH, we'll add
a small discrete inductor. We'll also have to add a resistor in
parallel with the transformer to damp the resonance, 330 ohms will
be about right. This looks like 53 ohms at the primary, and that
will be the amplifier's load at lower frequencies. The current
load may actually drop a bit near 10MHz, which is nice. This will
also help stabilize the amplifier, which would be unhappy driving
a purely-capacitive load.

. | A1
. |__________|\____ T1 ___________| E1+E4
. | | |/ | # | | |
. | inv #||# 330 | (Set 1)
. | | A2 #||# 10W |
. | |___|\____| #___|_______| E2+E3
. | |/ | |
. | AD815 | 1nF_|_
. | dc1 -,-
. | |___| E1+E4
. | ac sig 100k | |
. | bus ,--/\/--' (Set 2)
. | |
. | |___________| E2+E3
. | | |
. | dc2

You could build eight of these, each in its own little Pomona box,
mounted near its electrodes, to drive the entire linear trap. Or,
given the operation near the limit of the AD815, you could relax
the scene and make 16 of them... You could parallel amplifiers,
as shown in figure 50. Or you could make two sets in each box...

Fortunately the AD815 is cheap, under $10. I suggest the 15-Lead
through-hole SIP package, still available from Rochester, because
it's easier to heat sink (Pd = about 4 to 5 watts). The wideband
transformers will be small, inexpensive and easy to wind yourself.

Divide and conquer, eight or sixteen, that's my suggestion.
Click to expand...

I thought of something that interesting that might work if you wanted to
avoid the output transformer,
you could have a chain of amplifiers, each one bootstrapping the power
supply of the following amp.
Bit like a voltage multiplier or rather a charge pump.
Each amp output swing would add onto the previous stage, so for your nice
AD815 with 20v swing 5 stages would give you 100v swing.
each stage would nead a gain of g, 2, 3/2, 4/3.

However I got confused as to how much current each stage would take, first i
thought it would be the same, then I thought it would be twice as much, now
I think each stage might be the same after all (aprox), any thoughts ?

Instability might be an issue with the power supplies not being referenced
to ground if theres much stray capacitance to ground.
phase adjustment might be needed to keep each stage op in phase with its
power supply.


+15+---+
| |
| c* (rfc chokes or could use comon mode transformer)
| c
| c
| +-----+
| _|_ |
| -,- |
__|\___|____|\___ ... 3 more stages
|/ _|_ |/
| -,- |
| | |
| +-----+
| c
| c
| c*
| |
-15+---+


Colin =^.^=
 
J

john jardine

Winfield Hill said:
john jardine wrote...
Winfield wrote ...
[clip interesting stuff]
Second, we go looking for candidate amplifiers, such as the Analog
Devices' AD815. This is a dual amp, good for 50Vpp into 50 ohms
in bridge mode (500mA) up to 20MHz (G=2). See figure 52 in the
datasheet, http://www.analog.com/en/prod/0,2877,AD815,00.html
Click to expand...

Dammit, my lip's bleeding :).
I've now looked at this datasheet twice and still can't get my
head around the spec's being quoted.
How does figure 15, page 5, of the datasheet fit into the grand
scheme of things?.
Click to expand...

None. That means for example that Vos changes by 4mV as the output
swings to 6V, which is less than 0.1%, and of little concern here.
If you were making a precision A/D amplifier, it might be an issue.
Click to expand...

That's figure 12. ;)
regards
john
 
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