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If the Gm of the cross-coupled devices is smaller than the Gm of the diode-connected devices at the 1st stage it is not a latch, the cross-coupled devices are used to increase the gain.
Without cross-coupled devices the gain of the 1st stage is Au=Gm1,2/Gm3,4 (Gm1,2 corresponds to the diff.pair, Gm3,4 to the diode-connected loads).
With cross-coupled devices the gain of the 1st stage is Au=Gm1,2/(Gm3,4-Gm5,6) (Gm5,6 corresponds to the cross-coupled devices).
If Gm5,6 equals to Gm3,4 the gain will be infinite, if higher the 1st stage will act as a hysteresis comparator.
you can say this is a two-stage sense amplifier. The cross-coupled diode-connected load are multiplied as a current amplifier on the second stage. the two "extra" nmos are placed to increase the strength of pull-down. However, this circuit provides a negative transconductance and you can expect infinite gain from that point of view.
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