3 May 2017 Analytical and graphical techniques for solution of transistor circuit transfer functions
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Abstract
Modern Focal Plane Array (FPA) image sensors are highly-integrated, microelectronic processor chips comprising both analog and digital circuitry and are as complex as modern computer processor chips. A complete picture of how these devices operate requires a deep understanding of analog and digital microelectronic circuit analysis, and therefore, can be very intimidating to the engineer and/or project manager who is the end-user of the device in a system application. The overwhelming barrier to understanding how these devices work can be significantly lowered by analyzing the operation of individual sub-circuits that comprise the device. Here we will analyze a particular sub-circuit, the Source Follower (SF), which is used substantially in FPA designs as both a charge-to-voltage converter at the unit-cell (UC) input node as well as an all-purpose voltage buffering/level shifting element for driving subsequent circuit stages of low input impedance. The goal of this paper is to systematically analyze the Source Follower circuit using an equation -based approach. The analysis starts with the Sah equation which describes the DC (i.e. steady state) electrical operation of all Field Effect Transistors (FETs). Reasonable simplifications to the Sah equation then yield a tractable solution to the problem requiring only algebraic manipulation and use of the quadratic formula. Novel graphical techniques will also be used along with the resultant algebraic expressions to provide an intuitive feel for the circuit operation. The systematic approach taken here can provide useful tools and techniques for a novice in the field of microelectronic circuits who is interested in gaining a deeper understanding of FPA operation and/or analog-digital mixed-signal microelectronic designs.
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Bruce M. Lambert, "Analytical and graphical techniques for solution of transistor circuit transfer functions", Proc. SPIE 10209, Image Sensing Technologies: Materials, Devices, Systems, and Applications IV, 1020916 (3 May 2017); doi: 10.1117/12.2262224; https://doi.org/10.1117/12.2262224
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