J.Y. Yeom

A 12-channel CMOS preamplifier-shaper-discriminator ASIC for APD and gas counters

A 12-Channel (Ch) CMOS Preamplifier-Shaper-Discriminator ASIC designed for avalanche photodiode (APD) and gas counter readout has been fabricated on a 2.4 mmtimes2.4 mm die area using ROHM 0.35-muCMOS technology. This mixed signal ASIC consists of both analog and digital components and a window type discriminator is easily implemented through the use of a digital encoder to encode outputs from two comparators. The charge sensitive preamplifier is based on gain-boosted (regulated) cascode topology. The gain (voltage output to charge input) is 0.9 mV/fC and has been tested to have a low optimum Equivalent Noise Charge (ENC) of about 370 e-+30 e-/pF rms at a shaping time of 0.5 mus. The gain of the shaper is about 2.5 mV/fC and its peaking time can be varied from about 0.3 mus to 0.8 mus via an external pin. This chip is capable of sensing bipolar signals and is linear at least up to 320 fC for negative charge and 150 fC for positive charge. The average ENC of each channel has been calculated to be about 640 e -+30 e-/pF. The power consumption of the chip is approximately 0.13 W

Multichannel CMOS ASIC preamplifiers for avalanche photodiode and microstrip gas chamber readouts

A 10-channel (Ch) and a 16-Ch application specific integrated circuit (ASIC) preamplifier chip with telescopic-cascode topology and gain-boosted (regulated) cascode topology respectively has been designed for avalanche photodiode (APD) and microstrip gas chamber (MSGC) readouts. These highly integrated and reliable chips can be used for individual readouts from many channels to improve the spatial resolution and counting rate of such detectors over light sharing or charge division schemes. These chips were fabricated on a 2.4 times2.4 mm die area using ROHM 0.35-mu CMOS technology. The chips were tested to have a low optimum equivalent noise charge (ENC) of about 880 e

Design of new front-end electronics for animal PET

at a shaping time of 0.5 mus. The voltage output to charge input gains of the 10-Ch and 16-Ch preamplifiers are 0.71/pf and 0.91/pf while the rise times (10%-90%) are 15 and 13 ns, respectively. The 16-Ch chip was used to readout a GSO-APD detector and an optimum energy resolution of 11.3% (511 Kev peak of Na-22) was obtained while the coincidence time resolution with two such detectors is about 12.5 ns. The energy resolution of the 5.9 keV peak from a Fe-55 source obtained with a 3 times3 cm MSGC plate was about 20.5%

Development of a multi-channel waveform-sampling front-end ASIC and DOI detector for APD based animal PET

Highly pixilated detector modules for animal PET such as LSO-APD module require power-efficient, highly integrated and reliable front-end electronics. A new waveform sampling front-end chip for animal PET has been developed. The front-end electronics consist of a preamplifier, a variable gain amplifier (VGA) and a fast ADC per channel. The preamplifier picks up detector signals while the ADC samples the output signals of the preamplifier and converts them into digital waveforms. The VGA adjusts the signal amplitude to the maximum input range of the ADC. Digitizing the whole waveform on-chip would provide large flexibility for signal processing, e.g. the energy and time information can be extracted by either a simple linear interpolator or a more complex statistics estimator. The preamplifier, VGA and 6 bit 100 MSPS folding ADC have been designed using Rohm 0.35 /spl mu/m CMOS ASIC technology. Full custom ASIC technique allows us to integrate analog and digital circuits into one chip. The preamplifier occupies 180/spl times/100 /spl mu/m/sup 2/ and has a rise time of 22 ns while the VGA occupies 180/spl times/90 /spl mu/m/sup 2/ and have a variable gain from 3.6 to 25. The ADC occupies 0.24 mm/sup 2/ (excluding digital circuit), dissipates 1 W for 8 channels with a 3.3 V power supply and has a DNL of 0.7 LSB and INL of 1.4 LSB.

Development of a waveform sampling front-end ASIC for PET

A new multi-channel waveform sampling front-end (WSFE) application specific integrated circuit (ASIC) for positron emission tomography (I5ET) has been developed to digitize signals from scintillating crystals at an early stage to suppress noise while facilitating signal processing. Each channel of the chip consists of a preamplifier, a variable gain amplifier (VGA) and a fast analog to digital converter (ADC). This multi-channel chip will be used to readout each pixel of a phoswich detector based on GSO scintillators coupled individually to a multi-array avalanche photodiode (APD). Two WSFE ASIC have been developed together with some low noise preamplifiers in a separate chip.

A classification and verification of real pattern defects with dust filtering in tape substrate inspection

We present a versatile method for signal processing as an alternative to conventional methods using discrete front-end electronics. A new Waveform Sampling Front-End (WSFE) ASIC for Positron Emission Tomography (PET) has been developed to digitize signals at an early stage. Each channel of the chip consists of a preamplifier, a variable gain amplifier (VGA) and a fast Analog to Digital Converter (ADC) per channel. Two such chips have been designed and experimental results are presented in this paper.

Development of front end electronics for M-MSGC using individual-readout ASIC with resistive strip output

Tape substrate pattern of ultra-fine pitch circuit less than 10 micrometers in pattern width, is required to be inspected through high resolution optics. In the process of picking out defects at the level of the critical dimension through image processing, however, trivial blemishes formed by dust or micro particles may be detected simultaneously. This leads to unnecessary work on the part of operators reviewing and verifying the additional detected points. To maximize the efficiency of the inspection process, we need to identify and classify the defect candidates whether it is a real pattern defect or simply a trivial blemish by dust. Since a real defect arising from under or over etching bears inherent features in shape and brightness, it can thus be discriminated from other trivial blemishes. In this article, we propose an image feature based defect classification method, where proper measures were obtained from a series of image analysis with FFT. Based on the data collected from experiments, we devised a statistic model for classification.

Development of a Fast and High Resolution X-Ray Imaging Sensor for In-Line Inspection of Tape Substrate

A multi-grid-type microstrip gas chamber (M-MSGC) is being developed for the new spallation neutron source in Japan. The objective of this study is to provide a new position readout electronics for two-dimensional M-MSGC which can reduce the number of interconnections through a gas vessel by using a new encoding readout scheme based on ASIC technology. In order to test an ASIC based individual readout method, an ASIC chip, which has typically 16 individual input channels, has been designed and fabricated using a ROHM 0.35µ;m CMOS process and the chip was connected to a developed encoding circuit. The main results of the performance test indicated that the front-end electronics was able to encode 1500 pixels of the input position with 4.4% of position non-linearity. The results of this work confirm that the developed circuit would be appropriate for the front-end electronics of He-3 two-dimensional M-MSGC.

A fast and high resolution x-ray imaging sensor for tape substrate inspection

In an automated tape substrate inspections, machine vision is widely adopted for high throughput and cost advantages. However, conventional methods are overly sensitive to foreign particles or have limitations in detecting three-dimensional defects such as top over-etched defect. Foreign particles such as dustsdo not affect the integrity of the final product and are often detected as defects during inspection. To complement vision inspection systems, a prototype fast and fine spatial resolution X-ray imaging sensor has been developed. This image sensor, based on an optoelectronic device – the microchannel plate (MCP), has a spatial resolution of 20 μm and functions at frame rate of 30 fps. X-ray imaging is appropriate as it is virtually transparent to dust particles and provides information regarding the thickness of the copper wire patterns.

Characteristics of 16-Channel ASIC Preamplifier Board for Microstrip Gas Chamber and Animal PET

In automated Tape substrate (TS) inspection, machine vision is widely adopted for their high throughput and cost advantages. However, conventional methods are overly sensitive to foreign particles or have limitations in detecting three dimensional defects such as top over-etching. In an attempt to complement vision inspection systems, we proposed utilizing x-ray inspection. To implement x-ray inspection in TS application, we developed a prototype fast and high spatial resolution x-ray imaging sensor which functions at frame rate in excess of 30 fps and has a spatial resolution of 20 µm. In this paper, the development of the sensor and its performance is addressed and the efficiency of the x-ray inspection in detecting top over-etching defects will be shown with experimental studies.