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Astable multivibrator with MOSFET SPICE model

Started by Unknown January 29, 2016
Could some electronics guru point me to a working(i.e., correctly simulates) astable
multivibrator SPICE model with MOSFET only.
I have two working BJT based astable 
multivibrator SPICE models. However, my 
MOSFET based astable multivibrator model,
works as per hand calculation, but shows
no oscillations with a regular SPICE .TRAN
analysis. I have tried the standard SPICE 
tricks, as having voltage pulses on some 
nodes to kick start the oscillations, but 
these have no effect. Any hints, suggestions 
would be greatly appreciated. Thanks in advance.
On Thu, 28 Jan 2016 20:30:27 -0800 (PST), dakupoto@gmail.com wrote:

>Could some electronics guru point me to a working(i.e., correctly simulates) astable >multivibrator SPICE model with MOSFET only. >I have two working BJT based astable >multivibrator SPICE models. However, my >MOSFET based astable multivibrator model, >works as per hand calculation, but shows >no oscillations with a regular SPICE .TRAN >analysis. I have tried the standard SPICE >tricks, as having voltage pulses on some >nodes to kick start the oscillations, but >these have no effect. Any hints, suggestions >would be greatly appreciated. Thanks in advance.
Post your schematic. The usual transistor astable won't work if you just drop in mosfets. -- John Larkin Highland Technology, Inc lunatic fringe electronics
On Thu, 28 Jan 2016 20:30:27 -0800 (PST), dakupoto@gmail.com wrote:

>Could some electronics guru point me to a working(i.e., correctly simulates) astable >multivibrator SPICE model with MOSFET only. >I have two working BJT based astable >multivibrator SPICE models. However, my >MOSFET based astable multivibrator model, >works as per hand calculation, but shows >no oscillations with a regular SPICE .TRAN >analysis. I have tried the standard SPICE >tricks, as having voltage pulses on some >nodes to kick start the oscillations, but >these have no effect. Any hints, suggestions >would be greatly appreciated. Thanks in advance.
Post your schematic file (.ASC) ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | 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.
On Thursday, January 28, 2016 at 11:30:38 PM UTC-5, daku...@gmail.com wrote:
> Could some electronics guru point me to a working(i.e., correctly simulates) astable > multivibrator SPICE model with MOSFET only. > I have two working BJT based astable > multivibrator SPICE models. However, my > MOSFET based astable multivibrator model, > works as per hand calculation, but shows > no oscillations with a regular SPICE .TRAN > analysis. I have tried the standard SPICE > tricks, as having voltage pulses on some > nodes to kick start the oscillations, but > these have no effect. Any hints, suggestions > would be greatly appreciated. Thanks in advance.
Usually setting a nonzero voltage as an initial condition on the timing capacitor will start it up...
On Fri, 29 Jan 2016 08:45:21 -0800 (PST),
bloggs.fredbloggs.fred@gmail.com wrote:

>On Thursday, January 28, 2016 at 11:30:38 PM UTC-5, daku...@gmail.com wrote: >> Could some electronics guru point me to a working(i.e., correctly simulates) astable >> multivibrator SPICE model with MOSFET only. >> I have two working BJT based astable >> multivibrator SPICE models. However, my >> MOSFET based astable multivibrator model, >> works as per hand calculation, but shows >> no oscillations with a regular SPICE .TRAN >> analysis. I have tried the standard SPICE >> tricks, as having voltage pulses on some >> nodes to kick start the oscillations, but >> these have no effect. Any hints, suggestions >> would be greatly appreciated. Thanks in advance. > >Usually setting a nonzero voltage as an initial condition on the timing capacitor will start it up...
Unless both mosfets settle down to saturated. We need to see his circuit. -- John Larkin Highland Technology, Inc lunatic fringe electronics
On 29.1.16 18:54, John Larkin wrote:
> On Fri, 29 Jan 2016 08:45:21 -0800 (PST), > bloggs.fredbloggs.fred@gmail.com wrote: > >> On Thursday, January 28, 2016 at 11:30:38 PM UTC-5, daku...@gmail.com wrote: >>> Could some electronics guru point me to a working(i.e., correctly simulates) astable >>> multivibrator SPICE model with MOSFET only. >>> I have two working BJT based astable >>> multivibrator SPICE models. However, my >>> MOSFET based astable multivibrator model, >>> works as per hand calculation, but shows >>> no oscillations with a regular SPICE .TRAN >>> analysis. I have tried the standard SPICE >>> tricks, as having voltage pulses on some >>> nodes to kick start the oscillations, but >>> these have no effect. Any hints, suggestions >>> would be greatly appreciated. Thanks in advance. >> >> Usually setting a nonzero voltage as an initial condition on the timing capacitor will start it up... > > Unless both mosfets settle down to saturated. > > We need to see his circuit.
They will settle both on. The culprit is that there is no path for the timing capacitor charging current on the gate side when the gate is high. A MOS differs from a bipolar transistor or JFET (and also a tube) that there is no current via the gate when the transistor is turned fully on. The following thing works. The charge path is via diodes D7 and D8 in the Basic version. The price to pay is that the transistors do not turn fully on. Version 4 SHEET 1 1104 1448 WIRE -160 -176 -256 -176 WIRE -16 -176 -160 -176 WIRE 304 -176 -16 -176 WIRE 464 -176 304 -176 WIRE 768 -176 464 -176 WIRE -16 -144 -16 -176 WIRE 768 -144 768 -176 WIRE -16 -16 -16 -64 WIRE 48 -16 -16 -16 WIRE 192 -16 112 -16 WIRE 560 -16 192 -16 WIRE 640 -16 560 -16 WIRE 768 -16 768 -64 WIRE 768 -16 704 -16 WIRE 192 16 192 -16 WIRE 304 16 304 -176 WIRE 464 16 464 -176 WIRE 560 16 560 -16 WIRE -256 160 -256 -176 WIRE -16 160 -16 -16 WIRE 48 160 -16 160 WIRE 192 160 192 96 WIRE 192 160 112 160 WIRE 352 160 192 160 WIRE 464 160 464 96 WIRE 464 160 416 160 WIRE 624 160 464 160 WIRE 768 160 768 -16 WIRE 768 160 688 160 WIRE 880 160 768 160 WIRE -16 256 -16 160 WIRE 48 256 -16 256 WIRE 304 256 304 96 WIRE 304 256 112 256 WIRE 352 256 304 256 WIRE 560 256 560 96 WIRE 560 256 416 256 WIRE 624 256 560 256 WIRE 768 256 768 160 WIRE 768 256 688 256 WIRE -16 304 -16 256 WIRE 768 304 768 256 WIRE 192 384 192 160 WIRE 192 384 32 384 WIRE 560 384 560 256 WIRE 720 384 560 384 WIRE 560 432 560 384 WIRE 608 432 560 432 WIRE -256 448 -256 240 WIRE -16 448 -16 400 WIRE 768 464 768 400 WIRE -160 848 -160 -176 WIRE 0 848 -160 848 WIRE 208 848 0 848 WIRE 576 848 208 848 WIRE 784 848 576 848 WIRE 0 880 0 848 WIRE 208 880 208 848 WIRE 576 880 576 848 WIRE 784 896 784 848 WIRE 0 1024 0 960 WIRE 64 1024 0 1024 WIRE 208 1024 208 960 WIRE 208 1024 128 1024 WIRE 368 1024 208 1024 WIRE 784 1024 784 976 WIRE 784 1024 432 1024 WIRE 896 1024 784 1024 WIRE 0 1120 0 1024 WIRE 368 1120 0 1120 WIRE 576 1120 576 960 WIRE 576 1120 432 1120 WIRE 640 1120 576 1120 WIRE 784 1120 784 1024 WIRE 784 1120 704 1120 WIRE 0 1168 0 1120 WIRE 784 1168 784 1120 WIRE 208 1248 208 1024 WIRE 208 1248 48 1248 WIRE 576 1248 576 1120 WIRE 736 1248 576 1248 WIRE 576 1296 576 1248 WIRE 624 1296 576 1296 WIRE 0 1312 0 1264 WIRE 784 1328 784 1264 FLAG 768 464 0 FLAG -16 448 0 FLAG -256 448 0 FLAG 608 432 g1 FLAG 880 160 Out1 IOPIN 880 160 Out FLAG 784 1328 0 FLAG 0 1312 0 FLAG 624 1296 g3 FLAG 896 1024 Out2 IOPIN 896 1024 Out SYMBOL nmos 720 304 R0 SYMATTR InstName M1 SYMATTR Value 2N7002 SYMBOL nmos 32 304 M0 SYMATTR InstName M2 SYMATTR Value 2N7002 SYMBOL res -32 -160 R0 SYMATTR InstName R1 SYMATTR Value 1k SYMBOL res 752 -160 R0 SYMATTR InstName R2 SYMATTR Value 1k SYMBOL res 176 0 R0 SYMATTR InstName R3 SYMATTR Value 100k SYMBOL res 544 0 R0 SYMATTR InstName R4 SYMATTR Value 100k SYMBOL diode 704 -32 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName D1 SYMATTR Value 1N4148 SYMBOL diode 48 0 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D2 SYMATTR Value 1N4148 SYMBOL voltage -256 144 R0 SYMATTR InstName V1 SYMATTR Value 5 SYMBOL diode 624 272 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D3 SYMATTR Value 1N4148 SYMBOL diode 112 144 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName D4 SYMATTR Value 1N4148 SYMBOL res 288 0 R0 SYMATTR InstName R5 SYMATTR Value 10k SYMBOL res 448 0 R0 SYMATTR InstName R6 SYMATTR Value 10k SYMBOL diode 624 176 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D5 SYMATTR Value 1N4148 SYMBOL diode 112 240 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName D6 SYMATTR Value 1N4148 SYMBOL cap 416 144 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C1 SYMATTR Value 1n SYMBOL cap 416 240 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C2 SYMATTR Value 1n SYMBOL nmos 736 1168 R0 SYMATTR InstName M3 SYMATTR Value 2N7002 SYMBOL nmos 48 1168 M0 SYMATTR InstName M4 SYMATTR Value 2N7002 SYMBOL res -16 864 R0 SYMATTR InstName R7 SYMATTR Value 1k SYMBOL res 768 880 R0 SYMATTR InstName R8 SYMATTR Value 1k SYMBOL res 192 864 R0 SYMATTR InstName R9 SYMATTR Value 100k SYMBOL res 560 864 R0 SYMATTR InstName R10 SYMATTR Value 100k SYMBOL diode 640 1136 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName D8 SYMATTR Value 1N4148 SYMBOL diode 128 1008 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName D7 SYMATTR Value 1N4148 SYMBOL cap 432 1008 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C3 SYMATTR Value 1n SYMBOL cap 432 1104 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C4 SYMATTR Value 1n TEXT 304 368 Left 2 !.tran 1m TEXT 304 400 Left 2 !.ic V(g1)=3 TEXT 320 1264 Left 2 !.ic V(g3)=3 TEXT 288 736 Left 5 ;Basic TEXT 256 -280 Left 5 ;Complete RECTANGLE Normal -316 680 1096 1444 2 RECTANGLE Normal -320 564 1088 -360 2 -- -TV
On 29/01/16 17:54, John Larkin wrote:
> On Fri, 29 Jan 2016 08:45:21 -0800 (PST), > bloggs.fredbloggs.fred@gmail.com wrote: > >> On Thursday, January 28, 2016 at 11:30:38 PM UTC-5, daku...@gmail.com wrote: >>> Could some electronics guru point me to a working(i.e., correctly simulates) astable >>> multivibrator SPICE model with MOSFET only. >>> I have two working BJT based astable >>> multivibrator SPICE models. However, my >>> MOSFET based astable multivibrator model, >>> works as per hand calculation, but shows >>> no oscillations with a regular SPICE .TRAN >>> analysis. I have tried the standard SPICE >>> tricks, as having voltage pulses on some >>> nodes to kick start the oscillations, but >>> these have no effect. Any hints, suggestions >>> would be greatly appreciated. Thanks in advance. >> >> Usually setting a nonzero voltage as an initial condition on the timing capacitor will start it up... > > Unless both mosfets settle down to saturated. > > We need to see his circuit. > >
Here are two that work. You won't like it. Jeroen Belleman =========================== Version 4 SHEET 1 1192 680 WIRE -80 -96 -272 -96 WIRE 96 -96 -80 -96 WIRE 240 -96 96 -96 WIRE 416 -96 240 -96 WIRE 864 -96 416 -96 WIRE 1088 -96 864 -96 WIRE -80 -64 -80 -96 WIRE 96 -64 96 -96 WIRE 240 -64 240 -96 WIRE 416 -64 416 -96 WIRE 864 -64 864 -96 WIRE 1088 -64 1088 -96 WIRE -272 32 -272 -96 WIRE 96 48 96 16 WIRE 112 48 96 48 WIRE 128 48 112 48 WIRE 240 48 240 16 WIRE 240 48 192 48 WIRE 768 64 704 64 WIRE 864 64 864 16 WIRE 864 64 848 64 WIRE 704 112 704 64 WIRE 944 112 704 112 WIRE 1040 112 1008 112 WIRE 1088 112 1088 16 WIRE 1088 112 1040 112 WIRE -80 128 -80 16 WIRE 128 128 -80 128 WIRE 384 128 192 128 WIRE 416 128 416 16 WIRE 416 128 384 128 WIRE 96 160 96 48 WIRE 416 160 416 128 WIRE 864 160 864 64 WIRE 992 160 864 160 WIRE 864 176 864 160 WIRE 1088 176 1088 112 WIRE -80 240 -80 128 WIRE -32 240 -80 240 WIRE 0 240 -32 240 WIRE 48 240 0 240 WIRE 240 240 240 48 WIRE 320 240 240 240 WIRE 368 240 320 240 WIRE 704 256 704 112 WIRE 752 256 704 256 WIRE 816 256 752 256 WIRE 992 256 992 160 WIRE 1040 256 992 256 WIRE -272 288 -272 112 WIRE 96 288 96 256 WIRE 416 288 416 256 WIRE 864 320 864 272 WIRE 1088 320 1088 272 WIRE 0 336 0 304 WIRE 0 336 -272 336 WIRE 320 336 320 304 WIRE 320 336 0 336 WIRE -272 352 -272 336 WIRE -272 448 -272 432 FLAG 96 288 0 FLAG -272 288 0 FLAG 416 288 0 FLAG -32 240 G1 FLAG 320 240 G2 FLAG 112 48 D1 FLAG 384 128 D2 FLAG -272 448 0 FLAG 1088 320 0 FLAG 864 320 0 FLAG 1040 112 D4 FLAG 752 256 G3 SYMBOL nmos 48 160 R0 SYMATTR InstName M1 SYMATTR Value 2N7002 SYMBOL res 80 -80 R0 SYMATTR InstName R1 SYMATTR Value 1k SYMBOL res -96 -80 R0 SYMATTR InstName R2 SYMATTR Value 100k SYMBOL voltage -272 16 R0 SYMATTR InstName V1 SYMATTR Value 10 SYMBOL nmos 368 160 R0 SYMATTR InstName M2 SYMATTR Value 2N7002 SYMBOL res 400 -80 R0 SYMATTR InstName R3 SYMATTR Value 1k SYMBOL res 224 -80 R0 SYMATTR InstName R4 SYMATTR Value 100k SYMBOL cap 192 112 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C1 SYMATTR Value 100n SYMBOL cap 192 32 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C2 SYMATTR Value 100n SYMBOL voltage -272 336 R0 SYMATTR InstName V2 SYMATTR Value 3 SYMBOL diode 304 240 R0 WINDOW 0 -33 66 Left 2 SYMATTR InstName D2 SYMBOL diode -16 240 R0 WINDOW 0 -40 61 Left 2 SYMATTR InstName D3 SYMBOL nmos 1040 176 R0 SYMATTR InstName M3 SYMATTR Value 2N7002 SYMBOL nmos 816 176 R0 SYMATTR InstName M4 SYMATTR Value 2N7002 SYMBOL res 1072 -80 R0 SYMATTR InstName R5 SYMATTR Value 1k SYMBOL res 848 -80 R0 SYMATTR InstName R6 SYMATTR Value 1k SYMBOL res 864 80 M270 WINDOW 0 32 56 VTop 2 WINDOW 3 0 56 VBottom 2 SYMATTR InstName R7 SYMATTR Value 100k SYMBOL cap 1008 96 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C3 SYMATTR Value 33n100n TEXT 88 376 Left 2 !.ic v(G1)=0 TEXT 48 -136 Left 2 !.tran 100m
On Fri, 29 Jan 2016 22:39:36 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:

>On 29/01/16 17:54, John Larkin wrote: >> On Fri, 29 Jan 2016 08:45:21 -0800 (PST), >> bloggs.fredbloggs.fred@gmail.com wrote: >> >>> On Thursday, January 28, 2016 at 11:30:38 PM UTC-5, daku...@gmail.com wrote: >>>> Could some electronics guru point me to a working(i.e., correctly simulates) astable >>>> multivibrator SPICE model with MOSFET only. >>>> I have two working BJT based astable >>>> multivibrator SPICE models. However, my >>>> MOSFET based astable multivibrator model, >>>> works as per hand calculation, but shows >>>> no oscillations with a regular SPICE .TRAN >>>> analysis. I have tried the standard SPICE >>>> tricks, as having voltage pulses on some >>>> nodes to kick start the oscillations, but >>>> these have no effect. Any hints, suggestions >>>> would be greatly appreciated. Thanks in advance. >>> >>> Usually setting a nonzero voltage as an initial condition on the timing capacitor will start it up... >> >> Unless both mosfets settle down to saturated. >> >> We need to see his circuit. >> >> > >Here are two that work. You won't like it. > >Jeroen Belleman > >=========================== >Version 4 >SHEET 1 1192 680 >WIRE -80 -96 -272 -96
[Full Listing at Message-ID: <n8gm6m$b43$1@gioia.aioe.org> ]
>SYMATTR Value 33n100n >TEXT 88 376 Left 2 !.ic v(G1)=0 >TEXT 48 -136 Left 2 !.tran 100m
2nd version is clever... bias "class-A" guarantees starting (in real life, though .TRAN doesn't always self-start). ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
On 29/01/16 22:56, Jim Thompson wrote:
> On Fri, 29 Jan 2016 22:39:36 +0100, Jeroen Belleman > <jeroen@nospam.please> wrote: > [...] >>>> On Thursday, January 28, 2016 at 11:30:38 PM UTC-5, daku...@gmail.com wrote: >>>>> Could some electronics guru point me to a working(i.e., correctly simulates) astable >>>>> multivibrator SPICE model with MOSFET only.
[...]
>> >> Here are two that work. You won't like it. >> >> Jeroen Belleman >> >> =========================== >> Version 4 >> SHEET 1 1192 680 >> WIRE -80 -96 -272 -96 > [Full Listing at Message-ID: <n8gm6m$b43$1@gioia.aioe.org> ] >> SYMATTR Value 33n100n >> TEXT 88 376 Left 2 !.ic v(G1)=0 >> TEXT 48 -136 Left 2 !.tran 100m > > 2nd version is clever... bias "class-A" guarantees starting (in real > life, though .TRAN doesn't always self-start). > > ...Jim Thompson >
The 2nd version more commonly done with logic inverters. Jeroen Belleman
On Fri, 29 Jan 2016 23:53:06 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:

>On 29/01/16 22:56, Jim Thompson wrote: >> On Fri, 29 Jan 2016 22:39:36 +0100, Jeroen Belleman >> <jeroen@nospam.please> wrote: >> [...] >>>>> On Thursday, January 28, 2016 at 11:30:38 PM UTC-5, daku...@gmail.com wrote: >>>>>> Could some electronics guru point me to a working(i.e., correctly simulates) astable >>>>>> multivibrator SPICE model with MOSFET only. >[...] >>> >>> Here are two that work. You won't like it. >>> >>> Jeroen Belleman >>> >>> =========================== >>> Version 4 >>> SHEET 1 1192 680 >>> WIRE -80 -96 -272 -96 >> [Full Listing at Message-ID: <n8gm6m$b43$1@gioia.aioe.org> ] >>> SYMATTR Value 33n100n >>> TEXT 88 376 Left 2 !.ic v(G1)=0 >>> TEXT 48 -136 Left 2 !.tran 100m >> >> 2nd version is clever... bias "class-A" guarantees starting (in real >> life, though .TRAN doesn't always self-start). >> >> ...Jim Thompson >> > >The 2nd version more commonly done with logic inverters. > >Jeroen Belleman
Yep, I do that all the time. I usually do the 3-inverter version, with lots of snap and always starts. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | 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.