VELA: A fast DEPFET readout circuit for the IXO mission

The concept of active pixel sensor based on depleted P-channel FET (DEPFET) has been developed to cope with the emerging requirements of low noise and speed. The DEPFET detector/amplifier [1], thanks to an intrinsic low anode capacitance, can provide excellent energy resolution and fast readout at the same time. However, in order to fully exploit the speed capability, it is necessary to develop a new readout electronics, which is different from the ones employed up to now. For this purpose, we have developed a new front-end ASIC, named VLSI Electronic for Astronomy (VELA). The implemented circuit operates the pixels in a new current readout configuration to implement an extremely fast readout. The current version of VELA reads out 64×64 DEPFET matrixes with unparalleled frame rate and excellent energy resolution. The circuit architecture, the working principle, and the VELA suitability for X-ray imaging will be shown.