LT Spice universal opamp

Started by March 2, 2020
In universalopamp2, what does the "rail" parameter do?

--

John Larkin         Highland Technology, Inc

The cork popped merrily, and Lord Peter rose to his feet.
"Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"

Am 02.03.2020 um 18:02 schrieb jlarkin@highlandsniptechnology.com:
> > In universalopamp2, what does the "rail" parameter do? >
Hello John, rail=0 (default) means the maximum and minimum output voltages will be the supply voltages. If you set rail=2, the maximum output voltage will be the positive supply voltage minus 2V and the minimum output voltage will be the negative supply voltage plus 2V. Best regards, Helmut
On Mon, 2 Mar 2020 18:34:34 +0100, Helmut Sennewald
<helmutsennewald@t-online.de> wrote:

>Am 02.03.2020 um 18:02 schrieb jlarkin@highlandsniptechnology.com: >> >> In universalopamp2, what does the "rail" parameter do? >> > >Hello John, > >rail=0 (default) means the maximum and minimum output voltages will be >the supply voltages. >If you set rail=2, the maximum output voltage will be the positive >supply voltage minus 2V and the minimum output voltage will be the >negative supply voltage plus 2V. > >Best regards, >Helmut
OK, symmetric voltage limit. Thanks. -- John Larkin Highland Technology, Inc The cork popped merrily, and Lord Peter rose to his feet. "Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"
On 2020-03-02 09:38, jlarkin@highlandsniptechnology.com wrote:
> On Mon, 2 Mar 2020 18:34:34 +0100, Helmut Sennewald > <helmutsennewald@t-online.de> wrote: > >> Am 02.03.2020 um 18:02 schrieb jlarkin@highlandsniptechnology.com: >>> >>> In universalopamp2, what does the "rail" parameter do? >>> >> >> Hello John, >> >> rail=0 (default) means the maximum and minimum output voltages will be >> the supply voltages. >> If you set rail=2, the maximum output voltage will be the positive >> supply voltage minus 2V and the minimum output voltage will be the >> negative supply voltage plus 2V. >> >> Best regards, >> Helmut > > > OK, symmetric voltage limit. Thanks. >
You could probably add a voltage source to its output, tap the feedback off after that, and that way arrive at the asymmetrical limits of a real opamp. With a defined Ri it might be even more realistic. -- Regards, Joerg http://www.analogconsultants.com/
onsdag den 4. marts 2020 kl. 00.17.03 UTC+1 skrev Joerg:
> On 2020-03-02 09:38, jlarkin@highlandsniptechnology.com wrote: > > On Mon, 2 Mar 2020 18:34:34 +0100, Helmut Sennewald > > <helmutsennewald@t-online.de> wrote: > > > >> Am 02.03.2020 um 18:02 schrieb jlarkin@highlandsniptechnology.com: > >>> > >>> In universalopamp2, what does the "rail" parameter do? > >>> > >> > >> Hello John, > >> > >> rail=0 (default) means the maximum and minimum output voltages will be > >> the supply voltages. > >> If you set rail=2, the maximum output voltage will be the positive > >> supply voltage minus 2V and the minimum output voltage will be the > >> negative supply voltage plus 2V. > >> > >> Best regards, > >> Helmut > > > > > > OK, symmetric voltage limit. Thanks. > > > > You could probably add a voltage source to its output, tap the feedback > off after that, and that way arrive at the asymmetrical limits of a real > opamp. With a defined Ri it might be even more realistic. >
why not add/subtract the voltage from the supply
On 2020-03-03 15:39, Lasse Langwadt Christensen wrote:
> onsdag den 4. marts 2020 kl. 00.17.03 UTC+1 skrev Joerg: >> On 2020-03-02 09:38, jlarkin@highlandsniptechnology.com wrote: >>> On Mon, 2 Mar 2020 18:34:34 +0100, Helmut Sennewald >>> <helmutsennewald@t-online.de> wrote: >>> >>>> Am 02.03.2020 um 18:02 schrieb jlarkin@highlandsniptechnology.com: >>>>> >>>>> In universalopamp2, what does the "rail" parameter do? >>>>> >>>> >>>> Hello John, >>>> >>>> rail=0 (default) means the maximum and minimum output voltages will be >>>> the supply voltages. >>>> If you set rail=2, the maximum output voltage will be the positive >>>> supply voltage minus 2V and the minimum output voltage will be the >>>> negative supply voltage plus 2V. >>>> >>>> Best regards, >>>> Helmut >>> >>> >>> OK, symmetric voltage limit. Thanks. >>> >> >> You could probably add a voltage source to its output, tap the feedback >> off after that, and that way arrive at the asymmetrical limits of a real >> opamp. With a defined Ri it might be even more realistic. >> > > why not add/subtract the voltage from the supply >
You could do that as well but then if you want to make it more realistic (with an Ri) that Ri could affect some innards of the opamp model. Unless the model is strictly behavioral where it might not matter. -- Regards, Joerg http://www.analogconsultants.com/