Application of Neuron MOS in Analog Design S F Al-sarawi D Abbott P H Cole Depañment of Electrical and Electronic Engineering, University of Adelaide, SA This paper demonstrates the design of a Schmitt trigger circuit and two controlled gain amplifiers using a neuron MOS transistor and based on key design parameters identified in this paper. Simulation results indicate the feasibility of using neuron MOS in designing analog circuits that have characteristics independent of process parameters. 1 What is a Neuron MOS Transistor? The neuron NIOS transistor (ruNlOS), recentlv discovered by Shibata and Ohmi [1] in 1991, simply uses capaci- tively coupled inputs onto a floating gate. The resulting output is simply a rveighted sum of the inputs, due to the capacitive input network, followed by a thresholding operation. The behaviour of the transistor resembles, very rvell, that of a biological neuron rvhere the turn-on of the transistor is parallelled by the firing of a neuron. In this respect, the device is called a neuron il4OSFET or a neu-N{OS (ru}IOS) for short. The structure, the symbol ancl the capacitance representation of the vNfOS transistor are shown in Figures 1.a-c. zN,IOS circuits operate s'ith mixecl mode analog/digital functions and can even perform Boolean logical operations that are dynamically reconfigurable. The use of zIIOS circuits rvill greatly increase functionalitylareal2l while still maintaining lo.¿' cost via the use of standard CN,IOS fabrication. In addition to neural networks the application areas v/ere ¡zNIOS v'ili have use are motion detectors [3,4,5] , monolithic imaging/compression, spatiaì light modulators (SLNIs) and optical neural arrays [6]. v, v" ",1 ",-L- S ÅÅ Å t It co T S D (u) (b) (.) Figure 1: (a) The basic structure of an n-¡uNfOS transistor, (b) its electronic symbol. (c) Capacitance rep- resentation of the zNIOS, where Cs is the sum of all the parasitic capacitances from the floating gate to the substrate including the floating gate to source. In the literature, most zNIOS circuits have employed digital inputs [7] , however a few groups have explored analog ¡zNIOS techniques [8]. In this paper new analog circuits built using zNIOS transistor are discussed. Section 2 will discuss briefly the key design parameters for the z\,IOS transistor. Section 3 will discuss a new design for a Schmitt trigger circuit that has its hysteresis width a function of capacitor ratios. Section 4 will discuss the design of controlled gain amplifier circuits in which gain is controlled by capacitor ratio ratþer than depending on process parameters. 2 Key Design Parameters for zMOS TYansistor This section will identify some of the main key design parameters that can be used in designing analog and digital circuitry using ruMOS transistor. MtcRo'97 123