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Electronic Devices and Circuit TheoryStudy report of chapter 6 to 8Bei jing jiao tong universityCollege:electrical engineeringStudent :hai weixiaoID:14291036Director:hongLiChapter 6Field-Effect TransistorsWe will have this definition:FET is a three terminal device used for variety of applications that match,to a large extent ,those of the BJT transistor.Common point and primary difference:They are all made by semiconductor(p-type and n-type materials)The primary difference between the two types oftransistors is the fact that:The BJT transistor is a current-controlled device as depicted in 6.1a ,whereas the JFET transistors is a voltage-controlled device as 6.1b.In other words ,the current (IC)is a direct function of the level of (IB).For the FET the current (ID) will be a function of the voltage (VGS) applied to the input circuit as shown .In each case the current of the output circuit is controlled by a parameter of the input circuit -----in one case ashown in 6.3.Note tha the major partWe can get some fact is thet when studying carefully:If V GS=0,when the instant the voltage V DD=V GS is applied.The electrons are drawn to the drain terminal ,establishing the conventional current I D with the defined directionof 6.5 ,The path of charge flow clearly reveals that the drain and source currents are equivalent (I D=I S). The flow of charge is relatively uninhibited and is limited solely by the resistance of the n-channel between drain and source .It is important to note that the depletion region is wider near the top of both p-type materials .Assuming a uniform resistance in the n-channel. The current I D will establish the voltage levels through the channel as indicated on the same figure.When door shut down ,the fact that I G=0 is an important characteristic of the JFET.In this time V DS=V P,we can get I D max=I DSSIf V GS<0,the same effect reflect the under of the n-channel,the depletionregion is wider than only this effect reflect on the top of n-channe,this means that the door will shut down more faster. We can see this picture :Voltage-controlled resistor:The region to the left of the pinch-off locus is referred to as the ohmic or voltage-controlled resistance region .In this region ,the JFET can actually be employed as a variable resistor whose resistance can control be the applied gate to source voltage .Note the 6.11that the slope of each curve and therefore the resistance of the device between drain and source for V DS <V P are a function of the applied voltage V GS .When V DS<V Pr d= r o/(1-V GS/V P)^2;r o is the resistance with V GS=0Vand r d is the resistance at a particular level of V GS.Symbols three formsTransfer CharacteristicsI D=I DSS*(1-V GS/V P)^2I Dss and V P is constans,V GS is control variable.When V GS=0V, I D=I DSSWhen V GS=V P,I D=0mA.Shorthand Method:I D=I DSS*(1-V GS/V P)^2=I DSS*（1-V P/2/V P）^2=I DSS(0.5)^2.Maximum RatingsThe maximum rating list usually appears at the beginning of the specification sheet, with the maximum voltage between specific terminals , maximum current levels ,and the maximum power dissipation level of the device. The specified maximum levels for V DS and V GS must not be exceeded at any point in the design operation of the device.P D=V DS*I DWe can get operating region:In fig.6.33,both V DS and V GS have been set at some positive voltage ,establishing the drain and the gate at a positive potential with respect to the source. As V GS i ncreases in magnitude ,the concentration of electrons near the Sio2 surfaces increases until eventually the include n-type region can support a measurable flow between drain and source .the level of Vgs that result in the significant increases in drain current is called the threshold voltage (V T)When V GS > V T,I D=K*(V GS-V T)^2K=I D(on)/(V GS(on)-V T)^2CMOSChapter7summaryIn this chapter, we studied the frequency response of transistor circuits. We determined the effects due to circuit capacitors, including coupling, bypass, and load capacitors, and also analyzed the expanded equivalent circuits of BJTs and FETs to determine the frequency response of the transistors.A time constant technique was developed so that Bode plots can be constructed without the need of deriving complex transfer functions. The high and low corner frequencies or 3DB frequencies can be determined directly from the time constants.Coupling and bypass capacitors affect the low-frequency characteristics of a circuit. In general, capacitance values in the microfarad range typically result in cutoff frequencies in the hertz or tens of hertz range. A load capacitor affects the range typically result in cutoff frequencies in the vicinity of a megahertz or higher.An expanded hybrid-πmodel for the bipolar transistor and a highfrequency model for the field-effect transistor were developed. The capacitances included in these models result in reduced transistor gain at high frequencies. The cutoff frequency is a figure of merit for the transistor and is defined as the frequency at which the magnitude of the current gain is unity.The Miller effect is a multiplication of the base-collector or gate-drain capacitance due to feedback between the output and input of the transistor circuit. The bandwidth of the amplifier is reduced by this effect. The common-emitter (common-source) amplifier, in general, shows the greatest effect of the Miller multiplication factor, so the bandwidth of this circuit is the smallest of the three basic types of the amplifiers. The common-base (common-gate) amplifier has a larger bandwidth because of a smaller Miller multiplication factor. The cascade configuration, a combination of common-emitter and common-base stages, combines the advantages of high gain and wide band-width. The emitter-follower (source-follower) amplifier generally has the largest bandwidth of the three basic amplifier configurations.1;2; ;3;4;Chapter8summaryIn this chapter, we analyzed and designed amplifiers and output stages capable of delivering a substantial amount of power to a load.The current, voltage, and power ratings of BJTs and MOSFETs were considered, and the safe operating area for the transistors was defined in terms of these and the safe operating area for the transistor is related to the limiting parameters. The maximum power rating of a transistor is related to the maximum allowed device temperature at which the device can operate without being damaged.In a class-A amplifier, the output transistor conducts 100 percent of the time. The theoretical maximum power conversion efficiency for a standard class-A amplifier is 25 percent. This efficiency can be theoretically increased to 50 percent by incorporating inductors r transformers in the class-A circuits.Class-B output stages are composed of complementary pairs oftransistors operating in a push-pull manner. In an ideal class-B operation, each output transistor conducts 50 percent of the time. For an idealized Class-B output stage, the theoretical maximum power conversion efficiency is 78.5 percent.1;2;3;。