LTSpice: Still 2-pole trouble

[Chris Carlen]

Hi:

Here is an example with the new 2-pole model. It seems to have trouble
with asymmetrical power rails:


Version 4
SHEET 1 880 928
WIRE -672 624 -672 592
WIRE -560 624 -560 592
WIRE 80 272 112 272
WIRE 80 304 80 272
WIRE 80 368 80 400
WIRE 80 400 112 400
WIRE -672 512 -672 464
WIRE -560 512 -560 464
WIRE 48 352 16 352
WIRE 16 352 16 400
WIRE 48 320 -16 320
WIRE 32 208 -16 208
WIRE -16 208 -16 320
WIRE -16 320 -64 320
WIRE 112 208 208 208
WIRE 208 208 208 336
WIRE 208 336 112 336
WIRE 208 336 272 336
WIRE -144 320 -208 320
WIRE -208 896 -208 864
WIRE -208 784 -208 672
WIRE 96 624 128 624
WIRE 96 656 96 624
WIRE 96 720 96 752
WIRE 96 752 128 752
WIRE -32 672 0 672
WIRE 48 560 0 560
WIRE 0 560 0 672
WIRE 0 672 64 672
WIRE 128 560 208 560
WIRE 208 560 208 688
WIRE 208 688 128 688
WIRE 208 688 272 688
WIRE 32 752 32 704
WIRE 32 704 64 704
WIRE -112 672 -208 672
WIRE -208 672 -208 320
FLAG -672 624 0
FLAG -560 624 0
FLAG 112 272 Vpos
FLAG 112 400 Vneg
FLAG -672 464 Vpos
FLAG -560 464 Vneg
FLAG 16 400 0
FLAG -208 896 0
FLAG 128 624 Vpos
FLAG 128 752 Vneg
FLAG 32 752 0
SYMBOL Opamps\\2pole 80 336 R0
WINDOW 38 34 27 Left 0
SYMATTR InstName U1
SYMBOL voltage -672 496 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 10
SYMBOL voltage -560 496 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V2
SYMATTR Value -5
SYMBOL res 16 224 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 0 56 VBottom 0
SYMATTR InstName R1
SYMATTR Value 10k
SYMBOL res -160 336 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 0 56 VBottom 0
SYMATTR InstName R2
SYMATTR Value 10k
SYMBOL voltage -208 768 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V3
SYMATTR Value SINE(0 15 50)
SYMBOL Opamps\\1pole 96 688 R0
WINDOW 38 22 36 Left 0
SYMATTR InstName U2
SYMBOL res 32 576 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 0 56 VBottom 0
SYMATTR InstName R3
SYMATTR Value 10k
SYMBOL res -128 688 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 0 56 VBottom 0
SYMATTR InstName R4
SYMATTR Value 10k
TEXT -666 776 Left 0 !.tran 60m



--
____________________________________
Christopher R. Carlen
Principal Laser/Optical Technologist
Sandia National Laboratories CA USA
crcarle@sandia.gov

 

[Mike Engelhardt]

* Copyright Š Linear Technology Corp. 2003. All rights reserved.
*
..subckt 2pole 1 2 3 4 5
S1 5 3 N002 5 Q
S2 4 5 5 N002 Q
A1 2 1 0 0 0 0 N003 0 OTA G={Avol/Rout} ref={Vos}
+ Iout={slew*Cout} Cout={Cout} en={en} enk={enk}
+ in={in} ink={ink} Vhigh=1e308 Vlow=-1e308 Rout={Rout}
C3 5 4 1p
C4 3 5 1p
S3 N002 0 4 N002 C
S4 0 N002 N002 3 C
R3 3 2 1G noiseless
G1 0 N002 N003 0 {1/Rout}
R1 3 N002 {2*Rout} noiseless
R2 N002 4 {2*Rout} noiseless
C1 N002 0 {X*Cout/Avol}
S5 0 N003 N003 3 C
S6 N003 0 4 N003 C
R4 3 1 1G noiseless
R5 1 4 1G noiseless
R6 2 4 1G noiseless
..model C SW(Ron=100 Roff=1T Vt=2 Vh=-1 noiseless)
..param Rout=100Meg
..param Cout={Avol/GBW/2/pi/Rout}
..model Q SW(Ron=10 Roff=10Meg Vt=0 Vh=-.1 Vser={Rail}
+ ilimit={Ilimit} noiseless)
..param Avol=1Meg GBW=10Meg Slew=10Meg rail=0 Vos=0 ilimit=25m
..param en=0 enk=0 in=0 ink=0 phimargin=45
..param X table(phimargin,29.4,3.5,32.1,2.9,33.8,2.6,35.8,2.3,
+38.1,2,40.9,1.7,43.2,1.5,45.9,1.3,49.2,1.1,53.2,0.9,58.2,0.7,
+64.7,0.5,73,0.3,86.1,0.05)
..ends 2pole

 

[Jim Thompson]

On 06 Nov 2003 17:11:05 GMT, "Mike Engelhardt" <pmte@concentric.net>
wrote:

* Copyright Š Linear Technology Corp. 2003. All rights reserved.
*
.subckt 2pole 1 2 3 4 5
S1 5 3 N002 5 Q
S2 4 5 5 N002 Q
[snip 26ą lines]
38.1,2,40.9,1.7,43.2,1.5,45.9,1.3,49.2,1.1,53.2,0.9,58.2,0.7,
+64.7,0.5,73,0.3,86.1,0.05)
.ends 2pole

What happened to the three-line OpAmp ?

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Chris Carlen]

Mike Engelhardt wrote:

* Copyright Š Linear Technology Corp. 2003. All rights reserved.
*
.subckt 2pole 1 2 3 4 5
S1 5 3 N002 5 Q
S2 4 5 5 N002 Q
A1 2 1 0 0 0 0 N003 0 OTA G={Avol/Rout} ref={Vos}
+ Iout={slew*Cout} Cout={Cout} en={en} enk={enk}
+ in={in} ink={ink} Vhigh=1e308 Vlow=-1e308 Rout={Rout}
C3 5 4 1p
C4 3 5 1p
S3 N002 0 4 N002 C
S4 0 N002 N002 3 C
R3 3 2 1G noiseless
G1 0 N002 N003 0 {1/Rout}
R1 3 N002 {2*Rout} noiseless
R2 N002 4 {2*Rout} noiseless
C1 N002 0 {X*Cout/Avol}
S5 0 N003 N003 3 C
S6 N003 0 4 N003 C
R4 3 1 1G noiseless
R5 1 4 1G noiseless
R6 2 4 1G noiseless
.model C SW(Ron=100 Roff=1T Vt=2 Vh=-1 noiseless)
.param Rout=100Meg
.param Cout={Avol/GBW/2/pi/Rout}
.model Q SW(Ron=10 Roff=10Meg Vt=0 Vh=-.1 Vser={Rail}
+ ilimit={Ilimit} noiseless)
.param Avol=1Meg GBW=10Meg Slew=10Meg rail=0 Vos=0 ilimit=25m
.param en=0 enk=0 in=0 ink=0 phimargin=45
.param X table(phimargin,29.4,3.5,32.1,2.9,33.8,2.6,35.8,2.3,
+38.1,2,40.9,1.7,43.2,1.5,45.9,1.3,49.2,1.1,53.2,0.9,58.2,0.7,
+64.7,0.5,73,0.3,86.1,0.05)
.ends 2pole

This one doesn't work with a 0 volt negative or positive rail.




--
____________________________________
Christopher R. Carlen
Principal Laser/Optical Technologist
Sandia National Laboratories CA USA
crcarle@sandia.gov

 

[Mike Engelhardt]

* Copyright Š Linear Technology Corp. 2003. All rights reserved.
*
..subckt 2pole 1 2 3 4 5
S1 5 3 N002 5 Q
S2 4 5 5 N002 Q
A1 2 1 0 0 0 0 N003 0 OTA G={.1*Avol/Rout} ref={Vos}
+ Iout={.1*slew*Cout} Cout={Cout} en={en} enk={enk}
+ in={in} ink={ink} Vhigh=1e308 Vlow=-1e308 Rout={Rout}
C3 5 4 1p
C4 3 5 1p
R3 3 2 1G noiseless
G1 0 N002 N003 0 {10/Rout}
R1 3 N002 {2*Rout} noiseless
R2 N002 4 {2*Rout} noiseless
C1 N002 0 {X*Cout/Avol}
S5 0 N003 N003 3 C
S6 N003 0 4 N003 C
R4 3 1 1G noiseless
R5 1 4 1G noiseless
R6 2 4 1G noiseless
..model C SW(Ron=100 Roff=1T Vt=2 Vh=-1 noiseless)
..param Rout=100Meg
..param Cout={Avol/GBW/2/pi/Rout}
..model Q SW(Ron=10 Roff=10Meg Vt=0 Vh=-.1 Vser={Rail}
+ ilimit={Ilimit} noiseless)
..param Avol=1Meg GBW=10Meg Slew=10Meg rail=0 Vos=0 ilimit=25m
..param en=0 enk=0 in=0 ink=0 phimargin=45
..param X table(phimargin,29.4,3.5,32.1,2.9,33.8,2.6,35.8,2.3,
+38.1,2,40.9,1.7,43.2,1.5,45.9,1.3,49.2,1.1,53.2,0.9,58.2,0.7,
+64.7,0.5,73,0.3,86.1,0.05)
..ends 2pole

 

[Chris Carlen]

Mike Engelhardt wrote:

* Copyright Š Linear Technology Corp. 2003. All rights reserved.
*
.subckt 2pole 1 2 3 4 5
S1 5 3 N002 5 Q
S2 4 5 5 N002 Q
A1 2 1 0 0 0 0 N003 0 OTA G={.1*Avol/Rout} ref={Vos}
+ Iout={.1*slew*Cout} Cout={Cout} en={en} enk={enk}
+ in={in} ink={ink} Vhigh=1e308 Vlow=-1e308 Rout={Rout}
C3 5 4 1p
C4 3 5 1p
R3 3 2 1G noiseless
G1 0 N002 N003 0 {10/Rout}
R1 3 N002 {2*Rout} noiseless
R2 N002 4 {2*Rout} noiseless
C1 N002 0 {X*Cout/Avol}
S5 0 N003 N003 3 C
S6 N003 0 4 N003 C
R4 3 1 1G noiseless
R5 1 4 1G noiseless
R6 2 4 1G noiseless
.model C SW(Ron=100 Roff=1T Vt=2 Vh=-1 noiseless)
.param Rout=100Meg
.param Cout={Avol/GBW/2/pi/Rout}
.model Q SW(Ron=10 Roff=10Meg Vt=0 Vh=-.1 Vser={Rail}
+ ilimit={Ilimit} noiseless)
.param Avol=1Meg GBW=10Meg Slew=10Meg rail=0 Vos=0 ilimit=25m
.param en=0 enk=0 in=0 ink=0 phimargin=45
.param X table(phimargin,29.4,3.5,32.1,2.9,33.8,2.6,35.8,2.3,
+38.1,2,40.9,1.7,43.2,1.5,45.9,1.3,49.2,1.1,53.2,0.9,58.2,0.7,
+64.7,0.5,73,0.3,86.1,0.05)
.ends 2pole

Thanks Mike!

--
____________________________________
Christopher R. Carlen
Principal Laser/Optical Technologist
Sandia National Laboratories CA USA
crcarle@sandia.gov

 

[Helmut Sennewald]

"Mike Engelhardt" <pmte@concentric.net> schrieb im Newsbeitrag
news:boeb2e$907@dispatch.concentric.net...

* Copyright Š Linear Technology Corp. 2003. All rights reserved.
*
.subckt 2pole 1 2 3 4 5
S1 5 3 N002 5 Q
S2 4 5 5 N002 Q
A1 2 1 0 0 0 0 N003 0 OTA G={.1*Avol/Rout} ref={Vos}
....

Hello Mike,
where can I find a help on "OTA" and its parameters.
A1 2 1 0 0 0 0 N003 0 OTA G={.1*Avol/Rout} ref={Vos}
OTA = operational transconductance amplifier?
Other parameters for OTA?

Are there more useful A-devices we can't see in the help file
of LTSPICE?

Best Regards
Helmut

 

[Mike Engelhardt]

Helmut,

OTA = operational transconductance amplifier?

Yes.

where can I find a help on "OTA" and its parameters.
A1 2 1 0 0 0 0 N003 0 OTA G={.1*Avol/Rout} ref={Vos}
Other parameters for OTA? Are there more useful
A-devices we can't see in the help file
of LTSPICE?

Each A-device is an entry point to a compiler
whose definition changes with every release. The
definition changes to accommodate new SMPS models.
Basic devices like gates don't change, so they're
documented, first by examples and now also in the
help. The OTA's behavior won't change to break
the 1pole/2pole examples, but it's a pretty
complicated part that compiles expressions and
executes the object code at simulation time for
various aspects of their behavior. It also
contains a small library of transfer functions.
The default is hyperbolic tangent like one gets
from a diff pair. The idea is to use a nonlinear
transconductance into the dominate pole to model
slew rate in a manner which will also exhibit
the onset of slew rate limited distortion below
the hard slew limit.

I've avoided documenting this device because it
would take a great deal of time to do so and it
would look strange because its default behavior
is pretty bizarre since it was originally written
to model an obscure error amp of a SMPS product.

There's about thirty major entry points to the
A-device compiler. The OTA is one and the gates
are another. Anybody who really wants to know
what these A-devices do would have to join
the commercial interest of the LTspice team and
help develop them. In the defense industry they
say, "I could tell you, but then I'll have to
kill you". Here it's a case of I could tell you,
but then I'd have to hire you.

Best Regards,

--Mike

 

[Helmut Sennewald]

"Mike Engelhardt" <pmte@concentric.net> schrieb im Newsbeitrag
news:boeojo$589@dispatch.concentric.net...

Helmut,

OTA = operational transconductance amplifier?

Yes.

where can I find a help on "OTA" and its parameters.
A1 2 1 0 0 0 0 N003 0 OTA G={.1*Avol/Rout} ref={Vos}
Other parameters for OTA? Are there more useful
A-devices we can't see in the help file
of LTSPICE?

Each A-device is an entry point to a compiler
whose definition changes with every release. The
definition changes to accommodate new SMPS models.
Basic devices like gates don't change, so they're
documented, first by examples and now also in the
help. The OTA's behavior won't change to break
the 1pole/2pole examples, but it's a pretty
complicated part that compiles expressions and
executes the object code at simulation time for
various aspects of their behavior. It also
contains a small library of transfer functions.
The default is hyperbolic tangent like one gets
from a diff pair. The idea is to use a nonlinear
transconductance into the dominate pole to model
slew rate in a manner which will also exhibit
the onset of slew rate limited distortion below
the hard slew limit.

Hello Mike,
thanks a lot for this information. It has been very helpful to
understand the simulation results.

I have made two example circuits containing all the gathered information
about A-OTA and your 2pole opamp model.
It can be downloaded from the LTSPICE user's group.
http://groups.yahoo.com/group/LTspice/files/lib/The%20A%20model%20OTA/
PS: You have to register if you want access it, but it's free.

Best Regards
Helmut