文档介绍：Fundamentals of RF Circuit Design with Low Noise Oscillators. Jeremy Everard
Copyright © 2001 John Wiley & Sons Ltd
ISBNs: 0-471-49793-2 (Hardback); 0-470-84175-3 (Electronic)
1
Transistor ponent
Models at Low and High
Frequencies
Introduction
Equivalent circuit device models are critical for the accurate design and modelling
of ponents including transistors, diodes, resistors, capacitors and inductors.
This chapter will begin with the bipolar transistor starting with the basic T and then
the π model at low frequencies and then show how this can be extended for use at
high frequencies. These models should be as simple as possible to enable a clear
understanding of the operation of the circuit and allow easy analysis. They should
then be extendible to include the ponents to enable accurate
optimisation. Note that knowledge of both the T and π models enables regular
switching between them for easier circuit manipulation. It also offers improved
insight.
As an example S21 for a bipolar transistor, with an fT of 5GHz, will be calculated
pared with the data sheet values at quiescent currents of 1 and 10mA. The
effect of incorporating ponents such as the base spreading resistance
and the emitter contact resistance will be shown demonstrating accuracies of a few
per cent.
The harmonic and third order intermodulation distortion will then be derived
mon emitter and differential amplifiers showing the removal of even order
terms during differential operation.
The chapter will then describe FETs, diode detectors, varactor diodes and
ponents illustrating the effects of parisitics in ponents.
2 Fundamentals of RF Circuit Design
It should be noted that this chapter will use certain parameter definitions which
will be explained as we progress. The full definitions will be shown in Chapter 2.
Techniques for equivalent ponent extraction are also included in
Chapter 2.
Transistor Models at Low Frequencies
‘T’ Model
Considerable i