In a nmos tx initially,if source,gate and substrate are

[victoria_jitesh]

In a nmos tx initially,if source,gate and substrate are at ground and there is a vds supply.what happens if the substrate is given a +ve or -ve voltage...

 

[sekapr]

When there is vds, and if the body is at -ve, the device will be off since there is no channel between source and drain. When you increase the body bias there will be a small diode current

 

[sachinmaheshwari]

firstly, since there is no gate volage channel will not be there so no current will flow and the device will be in cut-off with a -ve substrate(as it is nmos all holes will be attracted by the -ve substrate voltage, and reversed biased pn junction diode so no current flows)
now increasing the subtrate voltage to a +ve side result in a small diode current(drain and substrate form a forward biased pn junction diode) but the transistor will be cutoff.