LT Spice schmitt oscillator
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From: John Larkin on 8 Oct 2009 18:59 On Fri, 09 Oct 2009 00:14:09 +0200, stefano delfiore <stefanodelfiore.leva(a)libero.it> wrote: >John Larkin ha scritto: >> Does anybody have a working LT Spice netlist for a simple schmitt >> inverter/R-C oscillator? I tried one using the library schmitt >> inverter and get obscure sim errors, and I don't understand the HELP >> stuff. >> >> What's the third pin in the corner for? Ground? >> >> Thanks, >> >> John >> >Hello John, try this: > Thanks, Stefano, that works. All those device params have to be set up. Do you know what that extra pin is for? I doesn't seem to do anything. John
From: Joerg on 8 Oct 2009 20:02 Jim Thompson wrote: > On Thu, 08 Oct 2009 15:31:30 -0700, Joerg <invalid(a)invalid.invalid> > wrote: > >> John Larkin wrote: >>> Does anybody have a working LT Spice netlist for a simple schmitt >>> inverter/R-C oscillator? I tried one using the library schmitt >>> inverter and get obscure sim errors, and I don't understand the HELP >>> stuff. >>> >>> What's the third pin in the corner for? Ground? >>> >> Helmut Sennewald once told me here in the NG. If you want to use the >> library Schmitt add this to value2: >> >> Vhigh=5 Vt=2.5 Vh=1 >> >> and this in SpiceLine: >> >> Td=5n >> >> Accessible by right-clicking the part. Change those values according to >> the datasheet for the part you actually want to design around. > > Or use a real Schmidt model instead of behavioral ;-) > Yep, for timing-critical stuff you have to. But a simple oscillator is often ok. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Jim Thompson on 8 Oct 2009 20:13 On Thu, 08 Oct 2009 17:02:03 -0700, Joerg <invalid(a)invalid.invalid> wrote: >Jim Thompson wrote: >> On Thu, 08 Oct 2009 15:31:30 -0700, Joerg <invalid(a)invalid.invalid> >> wrote: >> >>> John Larkin wrote: >>>> Does anybody have a working LT Spice netlist for a simple schmitt >>>> inverter/R-C oscillator? I tried one using the library schmitt >>>> inverter and get obscure sim errors, and I don't understand the HELP >>>> stuff. >>>> >>>> What's the third pin in the corner for? Ground? >>>> >>> Helmut Sennewald once told me here in the NG. If you want to use the >>> library Schmitt add this to value2: >>> >>> Vhigh=5 Vt=2.5 Vh=1 >>> >>> and this in SpiceLine: >>> >>> Td=5n >>> >>> Accessible by right-clicking the part. Change those values according to >>> the datasheet for the part you actually want to design around. >> >> Or use a real Schmidt model instead of behavioral ;-) >> > >Yep, for timing-critical stuff you have to. But a simple oscillator is >often ok. For accuracy and temperature stability far better than attainable with a Schmidt, use unbuffered inverters... http://analog-innovations.com/SED/CMOS-Osc-NoClip.pdf ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
From: Joerg on 8 Oct 2009 20:16 Jim Thompson wrote: > On Thu, 08 Oct 2009 17:02:03 -0700, Joerg <invalid(a)invalid.invalid> > wrote: > >> Jim Thompson wrote: >>> On Thu, 08 Oct 2009 15:31:30 -0700, Joerg <invalid(a)invalid.invalid> >>> wrote: >>> >>>> John Larkin wrote: >>>>> Does anybody have a working LT Spice netlist for a simple schmitt >>>>> inverter/R-C oscillator? I tried one using the library schmitt >>>>> inverter and get obscure sim errors, and I don't understand the HELP >>>>> stuff. >>>>> >>>>> What's the third pin in the corner for? Ground? >>>>> >>>> Helmut Sennewald once told me here in the NG. If you want to use the >>>> library Schmitt add this to value2: >>>> >>>> Vhigh=5 Vt=2.5 Vh=1 >>>> >>>> and this in SpiceLine: >>>> >>>> Td=5n >>>> >>>> Accessible by right-clicking the part. Change those values according to >>>> the datasheet for the part you actually want to design around. >>> Or use a real Schmidt model instead of behavioral ;-) >>> >> Yep, for timing-critical stuff you have to. But a simple oscillator is >> often ok. > > For accuracy and temperature stability far better than attainable with > a Schmidt, use unbuffered inverters... > > http://analog-innovations.com/SED/CMOS-Osc-NoClip.pdf > I mostly use them for PWM stuff where some "fuzz" on the slopes is desired, as long as the slopes are as steep as they can be. Sometimes adding even more fuzz is very beneficial at the EMC lab. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Joerg on 8 Oct 2009 20:34
John Larkin wrote: > On Fri, 09 Oct 2009 00:14:09 +0200, stefano delfiore > <stefanodelfiore.leva(a)libero.it> wrote: > >> John Larkin ha scritto: >>> Does anybody have a working LT Spice netlist for a simple schmitt >>> inverter/R-C oscillator? I tried one using the library schmitt >>> inverter and get obscure sim errors, and I don't understand the HELP >>> stuff. >>> >>> What's the third pin in the corner for? Ground? >>> >>> Thanks, >>> >>> John >>> >> Hello John, try this: >> > > Thanks, Stefano, that works. All those device params have to be set > up. > > Do you know what that extra pin is for? I doesn't seem to do anything. > That's "device common". Typically connected to ground, and all unused terminals are to be connected to device common. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |