Astable Multivibrator Generates Sub-Ground Voltages
Bookmark this page:
 Yahoo!
 Google
 Windows Live
 del.icio.us
 digg
 Netscape
|
|
||||||||||||||||
|
Posted by Jeff on November 5, 2005, 2:50 pm
Please log in for more thread options Hello, I've been simulating a circuit of the 'classic' astable multivibrator and analysing the results. This is the old-fashioned two-transistor design where each device (both NPNs) alternately turns off/on the other. I'm sure you know the type of thing. Anyway, the collector voltage of Q2 goes negative to almost the extent of the supply rail! Is this a Spice anomaly or would a real world circuit do the same? I don't see how it's possible for a circuit to generate sub-ground voltage levels. Isn't that theoretically impossible? The clock rate is 400Hz and Vcc is 5V. -Jeff. | ||||||||||||||||
|
Posted by Jim Thompson on November 5, 2005, 4:01 pm
Please log in for more thread options wrote: Which "Spice"? Can you post a schematic, either ASCII, or a real schematic (preferred) to alt.binaries.schematics.electronic ? ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food. | ||||||||||||||||
|
Posted by Jeff on November 5, 2005, 3:38 pm
Please log in for more thread options
Hi and thanks. I've just double-checked the simulation and it's actually the *bases* of both devices that go negative to -4.3V rather than the collectors, so my apologies. But the question still remains about how *any* node in such a circuit can go below GND. I will post the schematic if the above correction still doesn't account for what I'm seeing. -J. | ||||||||||||||||
|
Posted by Jim Thompson on November 5, 2005, 7:21 pm
Please log in for more thread options
wrote: >Hi and thanks.
>I've just double-checked the simulation and it's actually the *bases* >of both devices that go negative to -4.3V rather than the collectors, >so my apologies. But the question still remains about how *any* node in >such a circuit can go below GND. I will post the schematic if the above >correction still doesn't account for what I'm seeing. >-J. Capacitive coupling? ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food. | ||||||||||||||||
|
Posted by Jamie on November 5, 2005, 10:48 pm
Please log in for more thread options
Jeff wrote: > Hi and thanks.
sounds like the Cap Discharge effect.
> I've just double-checked the simulation and it's actually the *bases* > of both devices that go negative to -4.3V rather than the collectors, > so my apologies. But the question still remains about how *any* node in > such a circuit can go below GND. I will post the schematic if the above > correction still doesn't account for what I'm seeing. > -J. > -- Real Programmers Do things like this. http://webpages.charter.net/jamie_5 | ||||||||||||||||
| Similar Threads | Posted |
| Astable Multivibrator Generates Sub-Ground Voltages | November 5, 2005, 2:50 pm |
| Astable Multivibrator | May 21, 2006, 5:12 am |
| LM555 as a Astable Multivibrator help!! | July 17, 2006, 4:32 am |
| astable multivibrator issues - 2N3904s work, but not TIP31As | July 3, 2008, 6:25 pm |
| multivibrator | November 8, 2005, 11:25 pm |
| Monostable multivibrator | February 28, 2007, 3:42 pm |
| 555 astable problem | January 2, 2007, 3:46 pm |
| 555 Timer, Astable Oscillator Help | November 6, 2007, 11:25 am |
| Sweep Generator possible from 555 Astable circuit? | March 3, 2005, 10:30 pm |
| Metal to metal contact generates RF? | August 16, 2005, 3:49 pm |
| Where do you get those voltages? | August 3, 2006, 2:57 pm |
| Using Batteries For Odd Voltages | March 25, 2005, 11:30 am |
| UPS gives funny voltages - why? | May 27, 2005, 4:18 am |
| inverted voltages | October 9, 2006, 11:16 am |
| Multiplying and Dividing voltages | December 15, 2004, 4:12 am |
>
>I've been simulating a circuit of the 'classic' astable multivibrator
>and analysing the results. This is the old-fashioned two-transistor
>design where each device (both NPNs) alternately turns off/on the
>other. I'm sure you know the type of thing. Anyway, the collector
>voltage of Q2 goes negative to almost the extent of the supply rail! Is
>this a Spice anomaly or would a real world circuit do the same? I don't
>see how it's possible for a circuit to generate sub-ground voltage
>levels. Isn't that theoretically impossible? The clock rate is 400Hz
>and Vcc is 5V.
>
>-Jeff.