If the comparators bandwidth requirements are low enough, then an architecture, which differs from differential pairs, can be chosen as gain stage such as an open loop operational transconductance amplifier (OTA), which is shown in Fig.The analog voltage is sampled with the rising edge of the LATCH signal, which disconnects the inputs of the capacitors and connects the cross coupled structure to VDD and GND.Accordingly, the PCH device (MP1 or MP2) with the lower gate voltage will pull its drain voltage up. The outputs will be flipped to GND and VDD very quickly, which is shown in Fig.At 150 ns, where the input is positive, OUTP is pulled to VDD again in less than 3 ns.
Both structures, the OTA and the cross coupled latch, have their advantage.The OTA provides sufficient gain, so that the signal will reach digital signal levels and a standard flipflop can be used to strobe the signal.During the sampling process, the capacitors (OUTP and OUTN) are charged to the input voltages INP and INN.A good alternative to the OTA is a differential cross-coupled latch, which is shown exemplarily in Fig.2.41.2.42.2.42.2.43).