Forums

LT Spice opamp a liittle weird

Started by John Larkin May 1, 2017


I was wondering about the power dissipation of an opamp, driving a
sine wave into a mainly inductive load. See below.

The first few cycles current limit or something. I'm using
UniversalOpamp2 with current limit 2 amps and rail=0.

This opamp isn't documented in the HELP, or much anywhere else.

Peak current is under 700 mA, so why is it clipping?

Higher supply voltage helps.






Version 4
SHEET 1 880 680
WIRE 304 -64 224 -64
WIRE 224 -32 224 -64
WIRE 304 0 304 -64
WIRE 288 64 144 64
WIRE 224 96 224 48
WIRE 144 112 144 64
WIRE 192 112 144 112
WIRE 288 128 288 64
WIRE 288 128 256 128
WIRE 352 128 288 128
WIRE 384 128 352 128
WIRE 512 128 464 128
WIRE 544 128 512 128
WIRE 80 144 48 144
WIRE 192 144 80 144
WIRE 544 176 544 128
WIRE 48 208 48 144
WIRE 224 208 224 160
WIRE 48 320 48 288
WIRE 224 320 224 288
WIRE 544 320 544 256
FLAG 224 320 0
FLAG 544 320 0
FLAG 304 0 0
FLAG 48 320 0
FLAG 80 144 GEN
FLAG 352 128 AMP
FLAG 512 128 IND
SYMBOL res 368 144 R270
WINDOW 0 99 55 VTop 2
WINDOW 3 88 54 VBottom 2
SYMATTR InstName R1
SYMATTR Value 1
SYMBOL Opamps\\UniversalOpamp2 224 128 R0
WINDOW 0 37 43 Left 2
SYMATTR InstName U1
SYMATTR SpiceLine ilimit=2 rail=0 Vos=0 phimargin=45
SYMBOL voltage 224 304 R180
WINDOW 0 43 71 Left 2
WINDOW 3 44 38 Left 2
SYMATTR InstName V1
SYMATTR Value 12
SYMBOL voltage 224 64 R180
WINDOW 0 57 77 Left 2
WINDOW 3 57 42 Left 2
SYMATTR InstName V2
SYMATTR Value 12
SYMBOL voltage 48 192 R0
WINDOW 0 -79 47 Left 2
WINDOW 3 -199 89 Left 2
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V3
SYMATTR Value SINE(0 10 400)
SYMBOL ind 528 160 R0
WINDOW 0 72 41 Left 2
WINDOW 3 62 76 Left 2
SYMATTR InstName L1
SYMATTR Value 10m
TEXT -127 102 Left 2 !.tran 25m
TEXT -160 0 Left 2 ;Amp PdissTest
TEXT -152 48 Left 2 ;JL May 1, 2017

-- 

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement 

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

On Mon, 01 May 2017 18:12:28 -0700, John Larkin
<jjlarkin@highland_snip_technology.com> wrote:

> > > >I was wondering about the power dissipation of an opamp, driving a >sine wave into a mainly inductive load. See below. > >The first few cycles current limit or something. I'm using >UniversalOpamp2 with current limit 2 amps and rail=0. > >This opamp isn't documented in the HELP, or much anywhere else. > >Peak current is under 700 mA, so why is it clipping? > >Higher supply voltage helps. > > > > > > >Version 4 >SHEET 1 880 680 >WIRE 304 -64 224 -64 >WIRE 224 -32 224 -64 >WIRE 304 0 304 -64 >WIRE 288 64 144 64 >WIRE 224 96 224 48 >WIRE 144 112 144 64 >WIRE 192 112 144 112 >WIRE 288 128 288 64 >WIRE 288 128 256 128 >WIRE 352 128 288 128 >WIRE 384 128 352 128 >WIRE 512 128 464 128 >WIRE 544 128 512 128 >WIRE 80 144 48 144 >WIRE 192 144 80 144 >WIRE 544 176 544 128 >WIRE 48 208 48 144 >WIRE 224 208 224 160 >WIRE 48 320 48 288 >WIRE 224 320 224 288 >WIRE 544 320 544 256 >FLAG 224 320 0 >FLAG 544 320 0 >FLAG 304 0 0 >FLAG 48 320 0 >FLAG 80 144 GEN >FLAG 352 128 AMP >FLAG 512 128 IND >SYMBOL res 368 144 R270 >WINDOW 0 99 55 VTop 2 >WINDOW 3 88 54 VBottom 2 >SYMATTR InstName R1 >SYMATTR Value 1 >SYMBOL Opamps\\UniversalOpamp2 224 128 R0 >WINDOW 0 37 43 Left 2 >SYMATTR InstName U1 >SYMATTR SpiceLine ilimit=2 rail=0 Vos=0 phimargin=45 >SYMBOL voltage 224 304 R180 >WINDOW 0 43 71 Left 2 >WINDOW 3 44 38 Left 2 >SYMATTR InstName V1 >SYMATTR Value 12 >SYMBOL voltage 224 64 R180 >WINDOW 0 57 77 Left 2 >WINDOW 3 57 42 Left 2 >SYMATTR InstName V2 >SYMATTR Value 12 >SYMBOL voltage 48 192 R0 >WINDOW 0 -79 47 Left 2 >WINDOW 3 -199 89 Left 2 >WINDOW 123 0 0 Left 2 >WINDOW 39 0 0 Left 2 >SYMATTR InstName V3 >SYMATTR Value SINE(0 10 400) >SYMBOL ind 528 160 R0 >WINDOW 0 72 41 Left 2 >WINDOW 3 62 76 Left 2 >SYMATTR InstName L1 >SYMATTR Value 10m >TEXT -127 102 Left 2 !.tran 25m >TEXT -160 0 Left 2 ;Amp PdissTest >TEXT -152 48 Left 2 ;JL May 1, 2017
Submit your question to the LTspice List... I have no clue as to how Mikey's UniversalOpamp2 is supposed to work. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Thinking outside the box... producing elegant solutions. "It is not in doing what you like, but in liking what you do that is the secret of happiness." -James Barrie
On Tue, 02 May 2017 13:26:47 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

>On Mon, 01 May 2017 18:12:28 -0700, John Larkin ><jjlarkin@highland_snip_technology.com> wrote: > >> >> >> >>I was wondering about the power dissipation of an opamp, driving a >>sine wave into a mainly inductive load. See below. >> >>The first few cycles current limit or something. I'm using >>UniversalOpamp2 with current limit 2 amps and rail=0. >> >>This opamp isn't documented in the HELP, or much anywhere else. >> >>Peak current is under 700 mA, so why is it clipping? >> >>Higher supply voltage helps. >> >> >> >> >> >> >>Version 4 >>SHEET 1 880 680 >>WIRE 304 -64 224 -64 >>WIRE 224 -32 224 -64 >>WIRE 304 0 304 -64 >>WIRE 288 64 144 64 >>WIRE 224 96 224 48 >>WIRE 144 112 144 64 >>WIRE 192 112 144 112 >>WIRE 288 128 288 64 >>WIRE 288 128 256 128 >>WIRE 352 128 288 128 >>WIRE 384 128 352 128 >>WIRE 512 128 464 128 >>WIRE 544 128 512 128 >>WIRE 80 144 48 144 >>WIRE 192 144 80 144 >>WIRE 544 176 544 128 >>WIRE 48 208 48 144 >>WIRE 224 208 224 160 >>WIRE 48 320 48 288 >>WIRE 224 320 224 288 >>WIRE 544 320 544 256 >>FLAG 224 320 0 >>FLAG 544 320 0 >>FLAG 304 0 0 >>FLAG 48 320 0 >>FLAG 80 144 GEN >>FLAG 352 128 AMP >>FLAG 512 128 IND >>SYMBOL res 368 144 R270 >>WINDOW 0 99 55 VTop 2 >>WINDOW 3 88 54 VBottom 2 >>SYMATTR InstName R1 >>SYMATTR Value 1 >>SYMBOL Opamps\\UniversalOpamp2 224 128 R0 >>WINDOW 0 37 43 Left 2 >>SYMATTR InstName U1 >>SYMATTR SpiceLine ilimit=2 rail=0 Vos=0 phimargin=45 >>SYMBOL voltage 224 304 R180 >>WINDOW 0 43 71 Left 2 >>WINDOW 3 44 38 Left 2 >>SYMATTR InstName V1 >>SYMATTR Value 12 >>SYMBOL voltage 224 64 R180 >>WINDOW 0 57 77 Left 2 >>WINDOW 3 57 42 Left 2 >>SYMATTR InstName V2 >>SYMATTR Value 12 >>SYMBOL voltage 48 192 R0 >>WINDOW 0 -79 47 Left 2 >>WINDOW 3 -199 89 Left 2 >>WINDOW 123 0 0 Left 2 >>WINDOW 39 0 0 Left 2 >>SYMATTR InstName V3 >>SYMATTR Value SINE(0 10 400) >>SYMBOL ind 528 160 R0 >>WINDOW 0 72 41 Left 2 >>WINDOW 3 62 76 Left 2 >>SYMATTR InstName L1 >>SYMATTR Value 10m >>TEXT -127 102 Left 2 !.tran 25m >>TEXT -160 0 Left 2 ;Amp PdissTest >>TEXT -152 48 Left 2 ;JL May 1, 2017 > >Submit your question to the LTspice List...
Where's that? I have no clue as to how
>Mikey's UniversalOpamp2 is supposed to work.
I use it a lot, and it seems to work fine, but the current limit is really weird. If you ground the output, you get the limit that you specify. But the current limit declines as the output moves toward the rails; not ever super close to the rails. UOP2 is not mentioned in the LT Spice help. And not mentioned much anywhere else. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On Tue, 02 May 2017 13:39:57 -0700, John Larkin
<jjlarkin@highland_snip_technology.com> wrote:

>On Tue, 02 May 2017 13:26:47 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >>On Mon, 01 May 2017 18:12:28 -0700, John Larkin >><jjlarkin@highland_snip_technology.com> wrote: >> >>> >>> >>> >>>I was wondering about the power dissipation of an opamp, driving a >>>sine wave into a mainly inductive load. See below. >>> >>>The first few cycles current limit or something. I'm using >>>UniversalOpamp2 with current limit 2 amps and rail=0. >>> >>>This opamp isn't documented in the HELP, or much anywhere else. >>> >>>Peak current is under 700 mA, so why is it clipping? >>> >>>Higher supply voltage helps. >>> >>> >>> >>> >>> >>> >>>Version 4 >>>SHEET 1 880 680 >>>WIRE 304 -64 224 -64 >>>WIRE 224 -32 224 -64 >>>WIRE 304 0 304 -64 >>>WIRE 288 64 144 64 >>>WIRE 224 96 224 48 >>>WIRE 144 112 144 64 >>>WIRE 192 112 144 112 >>>WIRE 288 128 288 64 >>>WIRE 288 128 256 128 >>>WIRE 352 128 288 128 >>>WIRE 384 128 352 128 >>>WIRE 512 128 464 128 >>>WIRE 544 128 512 128 >>>WIRE 80 144 48 144 >>>WIRE 192 144 80 144 >>>WIRE 544 176 544 128 >>>WIRE 48 208 48 144 >>>WIRE 224 208 224 160 >>>WIRE 48 320 48 288 >>>WIRE 224 320 224 288 >>>WIRE 544 320 544 256 >>>FLAG 224 320 0 >>>FLAG 544 320 0 >>>FLAG 304 0 0 >>>FLAG 48 320 0 >>>FLAG 80 144 GEN >>>FLAG 352 128 AMP >>>FLAG 512 128 IND >>>SYMBOL res 368 144 R270 >>>WINDOW 0 99 55 VTop 2 >>>WINDOW 3 88 54 VBottom 2 >>>SYMATTR InstName R1 >>>SYMATTR Value 1 >>>SYMBOL Opamps\\UniversalOpamp2 224 128 R0 >>>WINDOW 0 37 43 Left 2 >>>SYMATTR InstName U1 >>>SYMATTR SpiceLine ilimit=2 rail=0 Vos=0 phimargin=45 >>>SYMBOL voltage 224 304 R180 >>>WINDOW 0 43 71 Left 2 >>>WINDOW 3 44 38 Left 2 >>>SYMATTR InstName V1 >>>SYMATTR Value 12 >>>SYMBOL voltage 224 64 R180 >>>WINDOW 0 57 77 Left 2 >>>WINDOW 3 57 42 Left 2 >>>SYMATTR InstName V2 >>>SYMATTR Value 12 >>>SYMBOL voltage 48 192 R0 >>>WINDOW 0 -79 47 Left 2 >>>WINDOW 3 -199 89 Left 2 >>>WINDOW 123 0 0 Left 2 >>>WINDOW 39 0 0 Left 2 >>>SYMATTR InstName V3 >>>SYMATTR Value SINE(0 10 400) >>>SYMBOL ind 528 160 R0 >>>WINDOW 0 72 41 Left 2 >>>WINDOW 3 62 76 Left 2 >>>SYMATTR InstName L1 >>>SYMATTR Value 10m >>>TEXT -127 102 Left 2 !.tran 25m >>>TEXT -160 0 Left 2 ;Amp PdissTest >>>TEXT -152 48 Left 2 ;JL May 1, 2017 >> >>Submit your question to the LTspice List... > >Where's that? > > >I have no clue as to how >>Mikey's UniversalOpamp2 is supposed to work. > > >I use it a lot, and it seems to work fine, but the current limit is >really weird. If you ground the output, you get the limit that you >specify. But the current limit declines as the output moves toward the >rails; not ever super close to the rails. > >UOP2 is not mentioned in the LT Spice help. And not mentioned much >anywhere else.
E-mail Helmut Sennewald <helmutsennewald@yahoo.com> and ask how to join... I can't remember how it's done since Yahoo @#$%'d up everything. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Thinking outside the box... producing elegant solutions. "It is not in doing what you like, but in liking what you do that is the secret of happiness." -James Barrie
On Mon, 01 May 2017 18:12:28 -0700, John Larkin
<jjlarkin@highland_snip_technology.com> wrote:

> > > >I was wondering about the power dissipation of an opamp, driving a >sine wave into a mainly inductive load. See below. > >The first few cycles current limit or something. I'm using >UniversalOpamp2 with current limit 2 amps and rail=0. > >This opamp isn't documented in the HELP, or much anywhere else. > >Peak current is under 700 mA, so why is it clipping? > >Higher supply voltage helps. > >
<snip Wouldn't it be more to the point to either use a model of a real part that does have recognizable current limiting behavior, or, if dissipation is the issue, disable the limiting function in the ideal model? RL
On Tue, 02 May 2017 18:46:33 -0400, legg <legg@nospam.magma.ca> wrote:

>On Mon, 01 May 2017 18:12:28 -0700, John Larkin ><jjlarkin@highland_snip_technology.com> wrote: > >> >> >> >>I was wondering about the power dissipation of an opamp, driving a >>sine wave into a mainly inductive load. See below. >> >>The first few cycles current limit or something. I'm using >>UniversalOpamp2 with current limit 2 amps and rail=0. >> >>This opamp isn't documented in the HELP, or much anywhere else. >> >>Peak current is under 700 mA, so why is it clipping? >> >>Higher supply voltage helps. >> >> ><snip > >Wouldn't it be more to the point to either use a model of a real part >that does have recognizable current limiting behavior, or, if >dissipation is the issue, disable the limiting function in the ideal >model? > >RL
Got a 2Amp OpAmp handy ?>:-} ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Thinking outside the box... producing elegant solutions. "It is not in doing what you like, but in liking what you do that is the secret of happiness." -James Barrie
On Tue, 02 May 2017 16:09:30 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

>On Tue, 02 May 2017 18:46:33 -0400, legg <legg@nospam.magma.ca> wrote: > >>On Mon, 01 May 2017 18:12:28 -0700, John Larkin >><jjlarkin@highland_snip_technology.com> wrote: >> >>> >>> >>> >>>I was wondering about the power dissipation of an opamp, driving a >>>sine wave into a mainly inductive load. See below. >>> >>>The first few cycles current limit or something. I'm using >>>UniversalOpamp2 with current limit 2 amps and rail=0. >>> >>>This opamp isn't documented in the HELP, or much anywhere else. >>> >>>Peak current is under 700 mA, so why is it clipping? >>> >>>Higher supply voltage helps. >>> >>> >><snip >> >>Wouldn't it be more to the point to either use a model of a real part >>that does have recognizable current limiting behavior, or, if >>dissipation is the issue, disable the limiting function in the ideal >>model? >> >>RL > >Got a 2Amp OpAmp handy ?>:-} > > ...Jim Thompson
I'm actually using a TCA0372, which is a dual 1-amp part. But I set the current limit to 1 amp in the UniversalOpamp2 model, and it limited way below 1 amp. The OnSemi data sheet says that it will output 1 amp, but doesn't say what the typ current limit is. Must be more. The cartoon schematic in the data sheet doesn't show any current limiting! So UniversalOpamp2 is fuzzy, and TCA0372 is fuzzy. Situation normal. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
>Got a 2Amp OpAmp handy ?>:-}
Sure thing--I have a couple of dozen LM675s in my drawer cabinet. Cheers Phil Hobbs
On Tue, 02 May 2017 16:09:30 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

>On Tue, 02 May 2017 18:46:33 -0400, legg <legg@nospam.magma.ca> wrote: > >>On Mon, 01 May 2017 18:12:28 -0700, John Larkin >><jjlarkin@highland_snip_technology.com> wrote: >> >>> >>> >>> >>>I was wondering about the power dissipation of an opamp, driving a >>>sine wave into a mainly inductive load. See below. >>> >>>The first few cycles current limit or something. I'm using >>>UniversalOpamp2 with current limit 2 amps and rail=0. >>> >>>This opamp isn't documented in the HELP, or much anywhere else. >>> >>>Peak current is under 700 mA, so why is it clipping? >>> >>>Higher supply voltage helps. >>> >>> >><snip >> >>Wouldn't it be more to the point to either use a model of a real part >>that does have recognizable current limiting behavior, or, if >>dissipation is the issue, disable the limiting function in the ideal >>model? >> >>RL > >Got a 2Amp OpAmp handy ?>:-} > > ...Jim Thompson
LT1210, with model in LSspice. RL
On Tuesday, May 2, 2017 at 4:26:55 PM UTC-4, Jim Thompson wrote:
> On Mon, 01 May 2017 18:12:28 -0700, John Larkin > <jjlarkin@highland_snip_technology.com> wrote: > > > > > > > > >I was wondering about the power dissipation of an opamp, driving a > >sine wave into a mainly inductive load. See below. > > > >The first few cycles current limit or something. I'm using > >UniversalOpamp2 with current limit 2 amps and rail=0. > > > >This opamp isn't documented in the HELP, or much anywhere else. > > > >Peak current is under 700 mA, so why is it clipping? > > > >Higher supply voltage helps. > > > > > > > > > > > > > >Version 4 > >SHEET 1 880 680 > >WIRE 304 -64 224 -64 > >WIRE 224 -32 224 -64 > >WIRE 304 0 304 -64 > >WIRE 288 64 144 64 > >WIRE 224 96 224 48 > >WIRE 144 112 144 64 > >WIRE 192 112 144 112 > >WIRE 288 128 288 64 > >WIRE 288 128 256 128 > >WIRE 352 128 288 128 > >WIRE 384 128 352 128 > >WIRE 512 128 464 128 > >WIRE 544 128 512 128 > >WIRE 80 144 48 144 > >WIRE 192 144 80 144 > >WIRE 544 176 544 128 > >WIRE 48 208 48 144 > >WIRE 224 208 224 160 > >WIRE 48 320 48 288 > >WIRE 224 320 224 288 > >WIRE 544 320 544 256 > >FLAG 224 320 0 > >FLAG 544 320 0 > >FLAG 304 0 0 > >FLAG 48 320 0 > >FLAG 80 144 GEN > >FLAG 352 128 AMP > >FLAG 512 128 IND > >SYMBOL res 368 144 R270 > >WINDOW 0 99 55 VTop 2 > >WINDOW 3 88 54 VBottom 2 > >SYMATTR InstName R1 > >SYMATTR Value 1 > >SYMBOL Opamps\\UniversalOpamp2 224 128 R0 > >WINDOW 0 37 43 Left 2 > >SYMATTR InstName U1 > >SYMATTR SpiceLine ilimit=2 rail=0 Vos=0 phimargin=45 > >SYMBOL voltage 224 304 R180 > >WINDOW 0 43 71 Left 2 > >WINDOW 3 44 38 Left 2 > >SYMATTR InstName V1 > >SYMATTR Value 12 > >SYMBOL voltage 224 64 R180 > >WINDOW 0 57 77 Left 2 > >WINDOW 3 57 42 Left 2 > >SYMATTR InstName V2 > >SYMATTR Value 12 > >SYMBOL voltage 48 192 R0 > >WINDOW 0 -79 47 Left 2 > >WINDOW 3 -199 89 Left 2 > >WINDOW 123 0 0 Left 2 > >WINDOW 39 0 0 Left 2 > >SYMATTR InstName V3 > >SYMATTR Value SINE(0 10 400) > >SYMBOL ind 528 160 R0 > >WINDOW 0 72 41 Left 2 > >WINDOW 3 62 76 Left 2 > >SYMATTR InstName L1 > >SYMATTR Value 10m > >TEXT -127 102 Left 2 !.tran 25m > >TEXT -160 0 Left 2 ;Amp PdissTest > >TEXT -152 48 Left 2 ;JL May 1, 2017 > > Submit your question to the LTspice List... I have no clue as to how > Mikey's UniversalOpamp2 is supposed to work. > > ...Jim Thompson > -- > | James E.Thompson | mens | > | Analog Innovations | et | > | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | > | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | > | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | > | E-mail Icon at http://www.analog-innovations.com | 1962 | > > Thinking outside the box... producing elegant solutions. > > "It is not in doing what you like, but in liking what you do that > is the secret of happiness." -James Barrie
LT spice on Yahoo groups... but it now fills up my gmail account. George H.