Utilizing a macromodel which calculates the floating gate potential by combining resistances and dependent voltage and current sources, DC transfer characteristics for multi-input neuron MOS inverters and for those in the neuron MOS full adder circuit are simulated both at room temperature and at 77 K. Based on the simulated results, low temperature circuit failures are discussed. Furthermore, circuit design parameter optimization both for low and room temperature operations is described.

A neuron MOS transistor has a floating gate and multiple input gates which are capacitively coupling with the floating gate. Dramatic reduction in the number of transistors and interconnections was achieved by employing the neuron MOS in circuit designs. Since the neuron MOS gate electrode is electrically floating, it is not necessarily easy to calculate the floating gate potential using circuit simulator SPICE. In order to simulate floating gate neuron MOS circuits, a macromodel which calculates the floating gate potential combining resistances and dependent voltage and current sources has been proposed. Eight kinds of neuron MOS circuits were designed and fabricated by a double polysilicon two level metal 1.2 µ m CMOS process. Utilizing SPICE, all the neuron MOS circuits were confirmed to operate correctly. The apparent threshold voltage as seen from the input gate in the 2-input n-channel neuron MOS transistor is arbitrarily changed by a control gate signal. Multi-input neuron MOS inverters and neuron MOS full adder circuits have been successfully simulated. Moreover, the effectiveness of the proposed macromodel has been experimentally verified by fabricated circuit measurements. Measured results confirmed that 3-input neuron MOS inverter outputs the low level when the number of input gates to which a high level is applied is more than half of all input gates.

A neuron-MOS transistor (νMOS) is applied to current-mode multi-valued logic (MVL) circuits. First, a novel low-voltage and low-power νMOS current mirror is presented. Then, a threshold detector and a quaternary T-gate using the proposed νMOS current mirrors are proposed. The minimum output voltage of the νMOS current mirror is decreased by VT (threshold voltage), compared with the conventional double cascode current mirror. The νMOS threshold detector is built on a νMOS current comparator originally composed of νMOS current mirrors. It has a high output swing and sharp transfer characteristics. The gradient of the proposed comparator output in the transfer region can be increased 6.3-fold compared with that in the conventional comparator. Along with improved operation of the novel current comparator, the discriminative ability of the proposed νMOS threshold detector is also increased. The performances of the proposed circuits are validated by HSPICE with Motorola 1.5 µm CMOS device parameters. Furthermore, the operation of a νMOS current mirror is also confirmed through experiments on test chips fabricated by VDEC*. The active area of the proposed νMOS current mirror is 63 µm 51 µm.

In this paper, a four-quadrant analog multiplier consisting of four neuron-MOS transistors and two load resistors is proposed. The proposed multiplier can be operated at only 1 V. Furthermore, the input range of the multiplier is equal to 100% of the supply voltage. The theoretical harmonic distortion caused by mobility degradation and device mismatchs is derived in detail. The performance of the proposed multiplier is characterized through HSPICE simulations with a standard 2.0 µm CMOS process with a double-poly layer. Simulations of the proposed multiplier demonstrate that the linearity error of 0.77% and a total harmonic distortion of 0.62% are obtained with full-scale input conditions. The maximum power consumption and 3 dB bandwidth are 9.56 µW and 107 MHz, respectively. The active area of the proposed multiplier is 210 µm 140 µm.

It is demonstrated that the enhancement in the functional capability of an elemental transistor is quite essential in developing human-like intelligent electronic systems. For this purpose we have introduced the concept of four-terminal devices. Four-terminal devices have an additional dimension in the degree of freedom in controlling currents as compared to the three-terminal devices like bipolar and MOS transistors. The importance of the four-terminal device concept is demonstrated taking the neuron MOS transistor (abbreviated as neuMOS or νMOS) and its circuit applications as examples. We have found that any Boolean functin can be realized by a two-stage configuratin of νMOS inverters. In addition, the variable threshold nature of the device allows us to build real-time reconfigurable logic circuits (no floating gate charging effect is involved in varying the threshold). Based on the principle, we have developed Soft-Hardware Logic Circuits and Real-Time Rule-Variable Data Matching Circuits. A winner-take-all circuit which finds the largest signal by hardware parallel processing has been also developed. The circuit is applied to building an associative memory which is different from Hopfield network in both principle and operation. The hardware algorithm in which binary, multivalue, and analog operations are merged at a very device level is quite essential to establish intelligent information processing systems based on highly flexible, real-time programmable hardwares realized by four-terminal devices.

We have developed a new functional MOS transistor called Neuron MOSFET (abbreviated as neuMOS or νMOS) which simulates the function of biological neurons. The new transistor is capable of executing a weighted sum calculation of multiple input signals and threshold operation based on the result of weighted summation, all in the voltage mode at a single transistor level. By utilizing its neuron-like very powerful functional capability, various circuits essential for multiple-valued logic operation have been designed using quite simple circuit configurations. The circuit designs for data conversion between the multivalued and binary logic systems and for generating universal literal functions are described and their experimental verifications are presented. One of the most important features of νMOS multivalued lagic circuit is that the circuit operates basically in the voltage mode, thus greatly reducing the power dissipation as compared to the conventional current mode circuitry. This is indeed most essential in implementing multivalued logic systems in ultra large scale integration. Another important feature of νMOS design is in its flexibility of implementing logic functions. The functional form of a universal literal function, for instance, can be arbitrarily altered by external signals without any modifications in its hardware configuration. A circuit representing multiple-valued multithreshold functions is also proposed.