The correcting transistor serves to maintain mirrored currents between each of the source transistors and {HEAD ~ each} of {TAIL ~ the sink transistors} to eliminate the implications of inequivalent voltage drop across corresponding series of transistors in the amplifier so that the range of output voltage swing, even in low supply voltage applications, closely approaches the value of the power supply voltage 
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The correcting transistor serves to maintain mirrored currents between each of the source transistors and { HEAD ~ each } of { TAIL ~ the sink transistors } to eliminate the implications of inequivalent voltage drop across corresponding series of transistors in the amplifier so that the range of output voltage swing , even in low supply voltage applications , closely approaches the value of the power supply voltage
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH