This document presents a linearity-saturation analysis for the IRCAM NICMOS3 detector. The plotted data are derived from the following data set:

1. Illumination: 72" dome broad-band flatfield lamps
2. Readout mode: CDS
3. Exposure times: 0.01 to 58 s
4. Filter: J
5. No dark count correction has been applied. The median dark rate is 0.42 DN/s, measured from a difference of 500 and 100 s frames.

Conclusions drawn:

1. The camera nonlinearity is significant below exposure times of 5 s. The reasons for this are under investigation.
2. Nonlinear saturation begins at a CDS-generated A/D signal of about 10,500 DN.
3. The flatfield lamp brightness is unstable on a timescale of minutes. This instability is not responsible for the low-end nonlinearity.