Larry_80 wrote on Feb 20th, 2013, 4:57pm:Hello Guys,
Please see attached circuits. The first on the LHS utilizes resistive feedback and the one on the RHS does not. I am driving a CONSTANT current load and capacitance. Could someone please explain if there is any advantage in using the Resistive feedback version over not using a resistive feedback? PSRR is of primary concern to me!
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If PSSR is a major concern, an item I have not seen mentioned is the manner in which the resistors are implemented and if they are adjustable using analog switches. Parasitic capacitance of either the resistors or the switches to the supply can significantly reduce the high frequency supply rejection. Hence, the use of the topology and substrate connections of resistors and any potential switches to adjust the resistor ratio, must be considered to optimize high frequency PSSR. It took me some time to track down this issue when it significantly reduced the PSSR of an LDO using a layout extracted view of the block when compared to its schematic view based simulation.