TABLE OF CONTENTS Objective: Modern digital circuits are implemented using almost exclusively MOS transistors. Therefore, to truly understand digital circuits, it is indispensable to know how MOS transistors are constructed and work, which is the purpose of this chapter. Basic circuit analysis is also included in the examples, as well as a special section on new MOS construction technologies for enhanced high-speed performance.
Chapter Contents
| 9.1 | Semiconductors |
| 9.2 | The Field-Effect Transistor (MOSFET) |
| 9.3 | I-V Characteristics |
| 9.4 | DC Response |
| 9.5 | CMOS Inverter |
| 9.6 | Transient Response |
| 9.7 | AC Response |
| 9.8 | Modern MOSFETs |
| 9.9 | Exercises |
| Note | The material presented below, previously seen in Section 8.1, is indispensable for a good understanding of the sections that follow. For that reason, it is repeated here. |
The preferred semiconductor for the fabrication of electronic devices is silicon (Si), because Si-based processes are more mature and cost less than other semiconductor processes. However, to construct transistors, diodes, or any other devices, the semiconductor must be "doped," which consists of introducing controlled amounts of other materials (called dopants) into the original semiconductor. In the case of Si, which has four valence electrons, such materials belong either to group III (like B, Al, Ga, In) or group V (P, As, Sb) of the periodic table.
Semiconductor doping is illustrated in Figure 9.1. In Figure 9.1(a), a dopant with five valence electrons (phosphorus, P) was introduced into the crystalline structure of Si. P forms four covalent bonds with neighboring Si atoms, leaving its fifth electron, which has a...
