dynamic two stage comparator

[dirac16]

In the following dynamic two stage comparator transistors Mx are used to connect the pre-amplifier stage to the latch stage. But are there any other purposes for Mx? In a well cited paper it was claimed that the transistors were used to provide a delay for the latch stage. They also added that this delay would help to increase the gain of the pre-amplifier stage. But how?

Image source: https://ieeexplore.ieee.org/document/5453302

 

[BradtheRad]

They also added that this delay would help to increase the gain of the pre-amplifier stage. But how?

Maybe it's not due to a change in gain, but rather reduced output when a load is applied as occurs at the end of the delay.

 

[sutapanaki]

Maybe because when CLK is 0 the outputs of the preamp are pulled to vdd and the sources of Mx are also pulled to vdd. When CLK goes high it will take some time for the preamp outputs to drop about Vth below vdd when Mx will start conducting. For that time the preamp develops its gain.

 

[guntherleet]

MX is like a buffer between the sensing stage to the latch stage. the differential input (INN/INP) create differential current discharging the capacitance on nets FN and FP in a rate ~(proportional) t , with the introduce of Mx the t required to activate the latch is longer then in different topology, this longer t create larger gain in terms of voltage separation on FN and FP