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about differential pmos input pair

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in p-sub process,as to the differential pmos input pair, the body can be connected to its source to eliminate body effect, and also body can be connected to vdd,
then can anybody tell me the other advantages and disadvantages of the two body connection?
thanks
 

connect to its source can improve pssr.
connect to vdd will be small area
 

connect to source will also eliminate the body effect and actually increase the gain.
 

Eliminating the body effect is the main advange when the body is connected to the source
 

connect to vdd can improve psrr,
connect to source can decrease offset,
 

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    newbie_1

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pmos input pair has many advanges such as slew rate,GB,1/f noise.
 

Sunking say that connect to source can improve psrr:cry:
arsenal said:
connect to vdd can improve psrr,
connect to source can decrease offset,
Click to expand...
 

connecting back gate to vdd will increase the the capacitance shunting the tail current source. This reduces output impedence of the tail current source at higher frequencies of common mode disturbance thereby degrading CM-DM performance of the diff amp.
 
connecting back gate to vdd will increase the the capacitance shunting the tail current source. This reduces output impedence of the tail current source at higher frequencies of common mode disturbance thereby degrading CM-DM performance of the diff amp.
Click to expand...

I agree. If the source and bulk of differential pair are connected together, the pn junction capacitance between n-well and p-sub will be also connnected to the source of couple-pair.
 

Another important advantage is, Commom mode range increases if you connect your body to Vdd in PMOS input diff amp.

I see this the main advantage you get if you connect it to vdd rather than to source.

Regards,
Prakash.
 

mainly for offset and improving pssr
 

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