Book contents
- Frontmatter
- Contents
- Preface
- 1 Introduction
- 2 Energy band basics
- 3 Electron and hole concentrations
- 4 Thermal equilibrium
- 5 Charge transport
- 6 np- and Np-junction basics
- 7 Solar cells
- 8 Light-emitting diodes
- 9 HBT basics
- 10 MOSFET basics
- 11 HJFET basics
- 12 Transistor capacitances
- 13 Transistors for high-speed logic
- 14 Transistors for high frequencies
- 15 Transistors for memories
- 16 Transistors for high power
- 17 Transistors for low noise
- 18 Transistors for the future
- Appendices
- Index
12 - Transistor capacitances
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Preface
- 1 Introduction
- 2 Energy band basics
- 3 Electron and hole concentrations
- 4 Thermal equilibrium
- 5 Charge transport
- 6 np- and Np-junction basics
- 7 Solar cells
- 8 Light-emitting diodes
- 9 HBT basics
- 10 MOSFET basics
- 11 HJFET basics
- 12 Transistor capacitances
- 13 Transistors for high-speed logic
- 14 Transistors for high frequencies
- 15 Transistors for memories
- 16 Transistors for high power
- 17 Transistors for low noise
- 18 Transistors for the future
- Appendices
- Index
Summary
The capacitance of a transistor is a crucial consideration when designing devices for applications in the commercially and societally important areas of digital logic, high-frequency signal processing, and memory. Accordingly, as a pre-cursor to the subsequent chapters on transistors suited to these applications, transistor capacitance is given a thorough treatment in this chapter of its own.
The approach taken presents capacitance in a general way that can be applied to all transistors. The usual practice is to treat capacitance in an ad hoc manner, sometimes involving charges of opposite polarity, as in junction capacitance, and sometimes considering just one polarity of charge, as in storage capacitance, for example. In fact, the origin of these two capacitances is the same: in the case of the emitter/base capacitance, for example, it is the change in charge within the device due to electrons that have entered from the emitter to set-up a new steady-state charge profile in the transistor in response to a change in base potential. This fact is recognized here, and provides a view of capacitance that is both physically based and intuitively appealing. Our approach is based on that of Tsividis for MOSFETs, and leads naturally to a double-subscripted specification of capacitance in all types of transistor, e.g., CEB or CSG. Thus, a 3×3 capacitance matrix captures all the capacitive elements of a three-terminal device, and allows for non-reciprocity.
- Type
- Chapter
- Information
- Understanding Modern Transistors and Diodes , pp. 210 - 224Publisher: Cambridge University PressPrint publication year: 2010