[SOLVED] Why -ve terminal of supply need to connect to ground????

[manalog]

Take an example of simple calculator:
- Calculator needs only one battery to run. ( Battery with one "+ve" & one "-ve" terminal).
- Calculator's body is usually made up of an insulator.
Does it mean the calculator doesn't need ground connection???

BUT, when I am doing a simulation with one MOS, along with Voltage source I need GND also!!!
My voltage source is already having an +ve & -ve terminals then why I need to connect -ve terminal to GND????

PLZ HELP...

 

[Teddy]

If you are in battery powered system like cellphone etc you "ground" connection is the battery - terminal.
In fact you can power whole system that you provide +20V and let say +17V from power supply to the - and + terminals of your pcb - it is all relative. You can also use -20V and -17V if you really want to play.
For simulation though it depends how the models and device macros were done. Usualy the global gnd! or gnd is used as a negative terminal. You MOS probably has bulk(body) connected to gnd in simulation model. - if you use 4 terminal MOS you should not have to connect gnd to -ve

- - - Updated - - -

If you are in battery powered system like cellphone etc you "ground" connection is the battery - terminal.
In fact you can power whole system that you provide +20V and let say +17V from power supply to the - and + terminals of your pcb - it is all relative. You can also use -20V and -17V if you really want to play.
For simulation though it depends how the models and device macros were done. Usualy the global gnd! or gnd is used as a negative terminal. You MOS probably has bulk(body) connected to gnd in simulation model. - if you use 4 terminal MOS you should not have to connect gnd to -ve

 

[Braski]

SPICE requires a node 0 to write the netlist, which is given by the (global) gnd. It is a convention, only a reference. All the voltages in the reality have sense only as "difference" from one node potential to another.

 

[manalog]

Thanks for your help "Teddy" & "Braski".