Bad PMOS with high Threshold Voltage

[joyce2002]

Hi Guys,

I have a question here.

I encountered one bad PMOS which requires 1.2V (Threshold Voltage) to turn on compared to a good PMOS which only requires 0.7V (Threshold Voltage) to turn on, in one of my failure analysis on a FPGA device.

I would like to find out what is the root cause which can cause the PMOS to turn on at a higher Vt.Could it due to the length of the channel between Drain and source? When the length of the channel increases, the resistance also increases, thus, more voltage is needed to drive electrons from drain to source? Eventually the Vt is higher in order for the transistor to turn on.

 

[ab_ba]

Hi
You can find precise description about this question in Analog circuit design B.Razavi.
Regards

 

[joyce2002]

Hi,

Could you explain further? I've already pre-order the book and it need some time before i can get the book.

Thanks!