  DEPFET pixel detectors are unique devices in terms of energy and spatial
resolution because very low noise (ENC = 2.2e at room temperature) operation
can be obtained by implementing the amplifying transistor in the pixel cell
itself. Full DEPFET pixel matrices have been built and operated for
autoradiographical imaging with imaging resolutions of 4.3 +- 0.8 um at 22 keV.
For applications in low energy X-ray astronomy the high energy resolution of
DEPFET detectors is attractive. For particle physics, DEPFET pixels are
interesting as low material detectors with high spatial resolution. For a
Linear Collider detector the readout must be very fast. New readout chips have
been designed and produced for the development of a DEPFET module for a pixel
detector at the proposed TESLA collider (520x4000 pixels) with 50 MHz line rate
and 25 kHz frame rate. The circuitry contains current memory cells and current
hit scanners for fast pedestal subtraction and sparsified readout. The imaging
performance of DEPFET devices as well as present achievements towards a DEPFET
vertex detector for a Linear Collider are presented.
