In this chapter, MATLAB will be used to solve problems involving metaloxide semiconductor field effect and bipolar junction transistors. The general topics to be discussed in this chapter are dc model of BJT and MOSFET, biasing of discrete and. | Attia John Okyere. Transistor Circuits. Electronics and Circuit Analysis using MATLAB. Ed. John Okyere Attia Boca Raton CRC Press LLC 1999 1999 by CRC PRESS LLC CHAPTER TWELVE TRANSISTOR CIRCUITS In this chapter MATLAB will be used to solve problems involving metaloxide semiconductor field effect and bipolar junction transistors. The general topics to be discussed in this chapter are dc model of BJT and MOSFET biasing of discrete and integrated circuits and frequency response of amplifiers. BIPOLAR JUNCTION TRANSISTORS Bipolar junction transistor BJT consists of two pn junctions connected back-to-back. The operation of the BJT depends on the flow of both majority and minority carriers. There are two types of BJT npn and pnp transistors. The electronic symbols of the two types of transistors are shown in Figure . Ic C B E Ie a b Figure a NPN transistor b PNP Transistor The dc behavior of the BJT can be described by the Ebers-Moll Model. The equations for the model are 1F 1 ES V VBE 1 exp -1 VBC Ï BC exp v -1 Ir ICS 1999 CRC Press LLC and Ic aFIF - IR IE - IF aRIR and IB 1 - Xf If 1 - Ur Ir where IES and ICS are the base-emitter and base-collector saturation currents respectively aR is large signal reverse current gain of a common-base configuration aF is large signal forward current gain of the common-base configuration. and kT VT ---- q where k is the Boltzmann s constant k x 10-23 o K T is the absolute temperature in degrees Kelvin and q is the charge of an electron q x 10-19 C . The forward and reverse current gains are related by the expression a I aR CS a I aF1 ES Is where IS is the BJT transport saturation current. The parameters aR and aF are influenced by impurity concentrations and junction depths. The saturation current IS can be expressed as 1999 CRC Press .
