First Readout of a 64 x 64 DEPFET Matrix With VELA Circuit

The new advancements in low-noise X-Ray detection pave the way to new space missions for deep space investigation like IXO. The concept of APS (Active Pixel Sensor) devices based on DEPFET (Depleted P-channel FET) structure has been developed to cope with the emerging requirements of low noise and high readout speed. Although the use of DEPFET makes achievable the required noise performance, it is necessary to develop a suitable front-end ASIC to fulfill the challenging speed requirements.We have developed VELA, a new fast multi-channel ASIC for the readout of a DEPFET matrix at high frame rate. The implemented circuit operates the DEPFET pixels in a drain current configuration to achieve a readout speed of 2 mu s per line or even faster.The current version of VELA integrates 64 analog channels to readout a 64 x 64 DEPFET matrix up to 7800 frames per second. In the paper, the circuit and the working principle are presented; the VELA performance and the first measurement with a 64 x 64 DEPFET matrix are also reported.