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Nguyên tắc cơ bản của thiết kế mạch RF với tiếng ồn thấp dao động P2

This chapter will describe the important linear parameters which are currently used to characterise two port networks. These parameters enable manipulation and optimisation of RF circuits and lead to a number of figures of merit for devices and circuits. Commonly used figures of merit include hFE, the short circuit low frequency current gain, fT, the transition frequency at which the modulus of the short circuit current gain equals one, GUM (Maximum Unilateral Gain), the gain when the device is matched at the input and the output and the internal feedback has been assumed to be zero | 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 2 Two Port Network Parameters 2.1 Introduction This chapter will describe the important linear parameters which are currently used to characterise two port networks. These parameters enable manipulation and optimisation of RF circuits and lead to a number of figures of merit for devices and circuits. Commonly used figures of merit include hFE the short circuit low frequency current gain f the transition frequency at which the modulus of the short circuit current gain equals one GUM Maximum Unilateral Gain the gain when the device is matched at the input and the output and the internal feedback has been assumed to be zero. All of these figures of merit give some information of device performance but the true worth of them can only be appreciated through an understanding of the boundary conditions defined by the parameter sets. The most commonly used parameters are the z y h ABCD and 5 parameters. These parameters are used to describe linear networks fully and are interchangeable. Conversion between them is often used as an aid to circuit design when for example conversion enables easy deconvolution of certain parts of an equivalent circuit. This is because the terminating impedance s and driving sources vary. Further if components are added in parallel the admittance parameters can be directly added similarly if they are added in series impedance parameters can be used. Matrix manipulation also enables easy conversion between for example common base common emitter and common collector configurations. For RF design the most commonly quoted parameters are the y h and 5 parameters and within this book familiarity with all three parameters will be required for circuit design. For low frequency devices the h and y parameters are quoted. At higher frequencies the 5 parameters hFE and fT are usually quoted. It