Bulk connection in a differential amplifier

[Chethan]

Hi,
can someone tell me where should the bulk of NMOS transistors be connected in a differential arrangement so as to eliminate body effect.

 

[suria3]

In the differential configuration, for the tail transistor, connect the bulk to the ground, so that the bulk and source are in the same potential. Whereby, for the input NMOS, you can apply the triple well transistor, so that you can tie bulk to source to minimize body effect. But normally, in desiging diff-amp, NMOS bulk is to connected to gnd.

 

[sunking]

it depond on you process.
if you use bicmos or p-well/SOI process, you can conncet you nmos bulk to its source. Or you have to connect it to gnd

 

[Chethan]

If i connect the bulk of NMOS to ground, then my source will be at a differential potential than the bulk.doesnt it introduce body effect. I am using the normal n well process with p substrate. is there any method where i can reduce the body effect.

 

[ccw27]

Yep there will be body effect. U can either use a triple well process or a PMOS input.

 

[jinxingsun]

U can use the PMOS input to achieve a better GB,slew rate and 1/f noise,but the gain will decrese.