Chapter 7Frequency ResponseIntroduction7.1 s-Domain analysis: poles,zeros and bode plots7.2theamplifiertransferfunction7.3 Low-frequency response of the common-sourceand common-emitter amplifier7.4 High-frequency response of the CS and CEamplifiers7.5 The CB, CG and cascode configurationsMicroelectronicCircuits
Microelectronic Circuits Chapter 7 Frequency Response Introduction 7.1 s-Domain analysis: poles,zeros and bode plots 7.2 the amplifier transfer function 7.3 Low-frequency response of the common-source and common-emitter amplifier 7.4 High-frequency response of the CS and CE amplifiers 7.5 The CB, CG and cascode configurations
ntroduction Why shall we study the frequency response?Actual transistors exhibit charge storagephenomena that limit the speed and frequency oftheir operation.频率失真.exeAims: the emphasis in this chapter is on analysisfocusing attention on the mechanisms that limitfrequency response and on methods for extendingamplifier bandwidth.MicroelectronicCircuits
Microelectronic Circuits Introduction ⚫ Why shall we study the frequency response? Actual transistors exhibit charge storage phenomena that limit the speed and frequency of their operation. ⚫ Aims: the emphasis in this chapter is on analysis. focusing attention on the mechanisms that limit frequency response and on methods for extending amplifier bandwidth
Three parts: s-Domain analysis and the amplifier transferfunction (April 13,2008) High frequency model of BJT and MOS;Low-frequency and High-frequency responseof the common-source and common-emitteramplifier (April 15,2008)Frequency response of cascode, Emitter andsource followers and differential amplifier(April 22,2008)MicroelectronicCircuits
Microelectronic Circuits Three parts: ⚫ s-Domain analysis and the amplifier transfer function (April 13,2008) ⚫ High frequency model of BJT and MOS; Low-frequency and High-frequency response of the common-source and common-emitter amplifier (April 15,2008) ⚫ Frequency response of cascode, Emitter and source followers and differential amplifier (April 22,2008)
Part I:s-Domain analysisZeros and polesBode plots The amplifier transfer functionMicroelectronic Circuits
Microelectronic Circuits Part I: ⚫ s-Domain analysis ⚫ Zeros and poles ⚫ Bode plots ⚫ The amplifier transfer function
7.1s-Domainanalysis-FregquencyResponseTransfer function: poles, zerosExamples: high pass and low passBode plots: Determining the 3-dBfrequencyMicroelectronic Circuits
Microelectronic Circuits 7.1 s-Domain analysis– Frequency Response ⚫ Transfer function: poles, zeros ⚫ Examples: high pass and low pass ⚫ Bode plots: Determining the 3-dB frequency
Transferfunction:poles,zerosMost of our work in this chapter will be concerned withfinding amplifier voltage gain as a transfer function ofthe complex frequency s.> A capacitance C: is equivalent an impedance 1/sC An inductance L: is equivalent an impedance SL> Voltage transfer function: by replacing S by jw, wecan obtain its magnitude response and phaseresponsem-1+...+aoT(s) = V.(s)/ V(s) =+br-isn-l +...+boYMicroelectronicCircuits
Microelectronic Circuits Transfer function: poles, zeros ➢ Most of our work in this chapter will be concerned with finding amplifier voltage gain as a transfer function of the complex frequency s. ➢ A capacitance C: is equivalent an impedance 1/SC ➢ An inductance L: is equivalent an impedance SL ➢ Voltage transfer function: by replacing S by jw, we can obtain its magnitude response and phase response 0 1 1 0 1 1 . . ( ) ( )/ ( ) s b s b a s a s a T s V s V s n n n m m m m o i + + + + + + = = − − − −
Transferfunction:poles,zeros(s - Z,)(s- Z,)......(s -ZmT(s) = V.(s)/V(s) = an(s - P)(s - P)......(s - P)Z1, Z2, ... Zm are called the transfer-function zeros ortransmission zeros.> P1, P2, ... Pm are called the transfer-function poles ornatural modes.The poles and zeros can be either real or complexnumbers, the complex poles(zeros) must occur inconjugate pairs.Microelectronic Circuits
Microelectronic Circuits Transfer function: poles, zeros ➢ Z1, Z2, . Zm are called the transfer-function zeros or transmission zeros. ➢ P1, P2, . Pm are called the transfer-function poles or natural modes. ➢ The poles and zeros can be either real or complex numbers, the complex poles(zeros) must occur in conjugate pairs. ( )( ).( ) ( )( ).( ) ( ) ( )/ ( ) 1 2 1 2 n m o i m s P s P s P s Z s Z s Z T s V s V s a − − − − − − = =
First-order Functions All the transfer functionsa,s+aoencountered in this chapterT(s)= have real poles and zeros ands+のocan be written as the product offirst-order transfer functionsao> Wo, called the pole frequency, isLow pass :T(s) =-s+0equal to the inverse of the timeconstant of circuita,sHigh pass : T(s) =network(STC).s+0oMicroelectronic Circuits
Microelectronic Circuits First-order Functions ➢ All the transfer functions encountered in this chapter have real poles and zeros and can be written as the product of first-order transfer functions. ➢ ω0, called the pole frequency, is equal to the inverse of the time constant of circuit network(STC). 0 1 0 ( ) + + = s a s a T s 0 1 0 0 High pass: ( ) Low pass: ( ) + = + = s a s T s s a T s
Example1:High pass circuit1A,Af0.707fiO+Q+(F)0f0.2p90°f00@ = 90°-arctan45°fi0°f(b)(a)R1joRCRCs7sT(s)11URCs +1S+1/ RCjoRC +1+RjoRCjwc11OLfrRC is the time constant; wL=1/RC2元2元T2元RCMicroelectronic Circuits
Microelectronic Circuits Example1: High pass circuit 2 1 + = • L L u f f f f A s RC s RCs RCs j RC j RC T s 1 1 1/ ( ) + = + = + = L f f = 90 − arctan RC is the time constant; ωL=1/RC
Example2: Low pass circuit1RO+ajac1IT十11+jaRCU;+ R0Ujac0O1/ RC[Aul S +1/ RC1RCisthetimeconstant;WH=1/RC0.70701LfH00°-45°f@=-arctan-90°fHMicroelectronic Circuits
Microelectronic Circuits Example2: Low pass circuit s RC RC T s 1/ 1/ ( ) + = H f f = −arctan RC is the time constant; ωH=1/RC 2 1 1 + = • H u f f A