Series of diode connected transistors

[deveshkm]

How is current determined in the branch if all transistors are diode connected?
Is it possible to determine the VGS across each of them, esp if it is possible that any of them could be in subthreshold

 

[esdeath_123]

How is current determined in the branch if all transistors are diode connected?
Is it possible to determine the VGS across each of them, esp if it is possible that any of them could be in subthreshold

Yes, you can determine VGS. Since it is diode-connected, the gate and drain are shorted, resulting to VGS=VDS. I'm not sure if it's possible for them to go into subthreshold since VDS+VTH>VGS for saturation, which would be true regardless of the value of VTH, so they can't be in subthreshold.

 

[vivekroy]

See the picture attached for the steps that I would have followed.

 

[KlausST]

Hi,

Since in a series connection the current is equal to all transistors you just need to calculate the voltage of one single transistor and multiply it with the transistor count.

But I don't know how your transistor is specified. Do you have a chart with gate voltage and drain current?

Klaus

 

[vivekroy]

Since in a series connection the current is equal to all transistors you just need to calculate the voltage of one single transistor and multiply it with the transistor count.

The threshold voltage can be different due to different bulk-source potentials.