A latch apparatus and applications thereof are provided. The latch apparatus consists of a latch circuit and a switchable DC block unit. The switchable DC block unit is coupled to the latch circuit, and configured to: isolate a cross-coupling path in the latch circuit and store a voltage difference before the latch apparatus performs the latching operation; and when the latch apparatus performs the latching operation, provide the stored voltage varying with time to increase the overdrive voltage of at least one transistor in the latch circuit (increase the transistor transconductance), so that the latch apparatus maintains high speed operation at low supply voltage.