Pixel-readout chips

Photograph of the CIC1 chip.

Pixel schematics.

The dynamic range of the integrator, calculated as the maximal signal range divided by the noise floor, is 118dB for 2.5ms measurement time.

The integrator noise is relatively constant - the SNR becomens very high for strong signals. For a signal of about 10000 charge units, the sigma noise is only about one charge unit. Charge unit = 6000 e. We can in this way distinguish 10000 from 10001 signals, etc.

The noise of the counting part without sensor is only about 33e.

CIC1

CIC1 is a pixel-readout chip for a hybrid pixel sensor. The chip contains a small matrix with 120 pixels of 120 x 120 micrometers size. Every pixel has the joint signal-counting and integrating capability. The chip is able to count the input charge pulses generated by e.g.photons and to measure the input charge flow at the same time. In this way, both, the number of the detected photons and their energy can be determined.

The integrator has very high and linear dynamic range - 1:800000 or 118 dB - the dynamic range is achievable within a single integration that takes 1.2 miliseconds. The integration is based on the simultaneous charge-to-time and charge-to-frequency conversion.

Possible applications are visible light detection for "multi-focal microscopy", medical x-ray imaging, diffraction x-ray imaging for crystallography, biology and medicine.

Results

The chip has been tested stand-alone and wire-bonded to a test pixel. During the stand-alone operation, the test circuits have been used to emulate the input signals. Counting rate of about 17MHz is possible. The dynamic range of the integrator is 118dB for 2.5ms measurement time. The signal response of the integrator is linear in the whole range. Moreover, the noise is quite constant - it does not increase much with the signal amplitude. The SNR becomens very high (about 10000) for strong signals. The noise of the counting part without sensor is only about 33e. The noise is slightly higher when the test pixel is used due to the non-ideal connection (a wire-bond is used instead a bump-bond). We measure a dynamic range of 114dB with the sensor for 2.5ms measurement time.