Performance evaluation of an architecture for the characterisation of photo-devices: design, fabrication and test on a CMOS technology

In this report, the performance of a particular pixel's architecture is evaluated. It consists mainly of an optical sensor coupled to an amplifier. The circuit contains photoreceptors such as phototransistors and photodiodes. The circuit integrates two main blocks: (a) the pixel architecture, c...

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Bibliographic Details
Published in:International journal of electronics 2011-03, Vol.98 (3), p.322-337
Main Authors: Castillo-Cabrera, G., García-Lamont, J., Reyes-Barranca, M.A., Moreno-Cadenas, J.A., Escobosa-Echavarría, A.
Format: Article
Language:English
Subjects:
Amplification
Amplifiers
Approximation
Architecture
Capacitance
Circuits
crosstalk
Current sources
Diodes
Electric currents
Electric power
photo-diodes
photo-transistors
Phototransistors
pixel architecture
Semiconductor devices
Simulation
spectral response
Transistors
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Summary:In this report, the performance of a particular pixel's architecture is evaluated. It consists mainly of an optical sensor coupled to an amplifier. The circuit contains photoreceptors such as phototransistors and photodiodes. The circuit integrates two main blocks: (a) the pixel architecture, containing four p-channel transistors and a photoreceptor, and (b) a current source for biasing the signal conditioning amplifier. The generated photocurrent is integrated through the gate capacitance of the input p-channel MOS transistor, then converted to voltage and amplified. Both input transistor and current source are implemented as a voltage amplifier having variable gain (between 10dB and 32dB). Considering characterisation purposes, this last fact is relevant since it gives a degree of freedom to the measurement of different kinds of photo-devices and is not limited to either a single operating point of the circuit or one kind and size of photo-sensor. The gain of the amplifier can be adjusted with an external DC power supply that also sets the DC quiescent point of the circuit. Design of the row-select transistor's aspect ratio used in the matrix array is critical for the pixel's amplifier performance. Based on circuit design data such as capacitance magnitude, time and voltage integration, and amplifier gain, characterisation of all the architecture can be readily carried out and evaluated. For the specific technology used in this work, the spectral response of photo-sensors reveals performance differences between phototransistors and photodiodes. Good approximation between simulation and measurement was obtained.
ISSN:0020-7217
1362-3060
DOI:10.1080/00207217.2010.538901