The 4-parameter logistic curve fit is the most common approach. It models a symmetric sigmoidal dose-response correlationship. The 5-parameter logistic fit function adds an asymmetry parameter. The 3-parameter models is a reduced 4-parameter model, where one of the asymptotes has to be set to a fixed value or to the mean of a control line, which allows the system to deal with truncated data.
PLA 3.0 allows you to carry out the regression for each standard/sample combination in your bioassay separately or at once.