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This paper presents two new general threshold gate (GTG) structures which are based on the monostable-bistable element (MOBILE) as their main part. These new GTGs eliminate an RTD from the structure compared to old structures and lead to less elements count and better performance in terms of power consumption, maximum frequency, and power-delay product (PDP). In the paper also two new single gate three-input XOR logic gates based on the old GTGs and two ones based on the new GTGs are presented and simulated in HSPICE simulator.

One of the most promising nanoscale devices expected to augment CMOS technology in future is the resonant-tunneling diode (RTD) that is the most mature technology of quantum nanoelectronics [

Threshold gate (TG) topology [

Implementing three-input XOR function in a single gate structure by old MOBILE topologies, such as TG and MTTG, were not practical [

In this letter for the first time, to the best of author’s knowledge, two modified versions for general threshold gate (GTG) topology, which is the newest member of MOBILE based topologies, are presented in order to implement logic functions. Then we introduce two three-input XOR gates in single gate structure based on generic GTG and two other ones based on our new modified versions of GTG.

The new designs are based on GTG topology. The input-output relationship for a generic GTG is shown in (

Equation (

(a) The proposed GTG-2 three-input XOR. RTD areas are

Equation (

As stated before, eliminating RTD(s) from GTG-based circuits would present new structures that we call them GTG-4 and GTG-5 which correspond to the modified GTG-2 and GTG-3, respectively (Figure

Selecting any higher value for the coefficient of this term does not change the result of the mentioned function and this coefficient is the only one that has this feature. Hence, if the inputs adjust to (111), the output would be equal to 1. Meanwhile, in the implemented circuit the drive RTD should be switched [

^{2}). By increasing the

This method is repeated for (

For the MOBILE-based circuits the RTD areas should be adjusted to appropriate values for correct operation; moreover, the transistors width may be tuned for better performance [

Figure

Comparison between single gates and cascaded gates of three-input XOR logic based on MOBILE structure. The results are normalized based on GTG-2 result except second column (PDP = (Power at

THREE-INPUT XOR TYPE | Device counts = RTD + Transistor | PDP | |
---|---|---|---|

Cascaded GTG-3 [ | 25 | 1 | 1 |

GTG-2 | 17 | 0.66 | 0.85 |

GTG-3 | 21 | 1.33 | 0.35 |

GTG-4 | 16 | 0.92 | 0.53 |

GTG-5 | 20 | 1.71 | 0.26 |

The simulation results for proposed XOR gate circuits. (a) The clock

The table shows that GTG-4 and GTG-5 designs have better performance in comparison with GTG-2 and GTG-3 in all aspects especially in PDP and all new designs have better performance in terms of device count.

In this paper we have introduced two modified structures for general threshold gate topology based on MOBILE. These two new structures eliminate RTDs and lead to lower power consumption, better speed, and PDP. Then we proposed two three-input XOR logic gates based on old GTG topologies and two based on new GTG topologies. Our designs also were compared with a different three-input XOR logic gate that consists of two cascaded, previously introduced, two-input XOR gates. The HSPICE simulation results showed that the three-input XOR based on GTG-5 is the best one according to maximum frequency and PDP and that one that is based on GTG-4 is the best in terms of device count.