Hi,
The excellent op am OPA820 is used as an error amplifier in an LDO circuitry. OPA820 is suppled by the +5v single supply. the LDO input is 3v3, and the output is setted as 3v0.The pass element is an N channel power MOSFET, its gate threshold voltage is 0.4~1v (max), it requires that OPA820output voltage must be 3v+1v+Vds at least as the MOSFET operates in Zone of saturation.
However, the OPA820 datasheet shows only +3.75v from 0c to 70c, and 3.7v from -40c to 85c (test condition: Rf=402Ohm. G=+2). The op amp output voltage is limited by the saturation voltage (bipolar) or the on resistance (CMOS) of the output transistors and the load being driven, The MOSFET driver current is very small, what is the maximum output voltage of the OPA820 when it is driving a very light load? Does TI have verification data or results? Base on my practice, OPA820 can have a 4.5v output, does OPA820 have 4.5v output voltage capability over all case (-5c to 75c )? THANKS.
