A modified Depleted P-Channel Field Effect Transistor (DEPFET) is the key feature of the DEPFET Sensor with Signal Compression (DSSC), a 1 Mpixel X-ray camera aiming at ultra-fast imaging of soft X-rays at the European XFEL. Operation of large-area devices with a large number of DSSC-type DEPFET pixels requires the accurate knowledge of the sensitivity of the response to the relevant DEPFET parameters. The paper presents the experimental qualification of the response of DSSC-type DEPFET pixels in the space of 4 relevant parameters: drain current, source voltage, drain voltage and back side voltage. The obtained results allow estimation of the impact of the inevitable parameter fluctuations in large monolithic sensors and of the actual trimming range of the shape of signal compression in view of the pixelwise calibration of the 1 Mpixel DSSC camera.