Designing 3-Dimensional NAND Circuits: Key Considerations

This lecture discusses the design of 3-dimensional NAND circuits, focusing on the challenges and solutions related to the sizing of PMOS and NMOS transistors. The instructor begins by analyzing an inverter circuit, highlighting the significant impact of capacitance on performance. A simulation demonstrates that the charging time is longer than the discharging time due to the lower mobility of holes in PMOS transistors compared to electrons in NMOS transistors. To address this, the instructor proposes increasing the width of the PMOS transistors to three times that of the NMOS transistors, resulting in balanced charging and discharging times. The lecture further explores the design of a NAND gate with three inputs, emphasizing the importance of transistor sizing in achieving optimal performance. The instructor also discusses the influence of parasitic capacitances and the need to consider internal capacitances in practical designs. The lecture concludes with a comprehensive overview of the factors affecting the performance of complex logic functions, providing valuable insights for circuit designers.