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EE 203 Lecture 12

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EE 203 Lecture 12 EE 330 Lecture 30 Basic amplifier architectures • Common Emitter/Source • Common Collector/Drain • Common Base/Gate Review from Previous Lecture Two-port representation of amplifiers Unilateral amplifiers: y V1 y11 22 V2 y21V1 • Thevenin equivalent output port often more standard • RIN, AV, and ROUT often used to characterize the two-port of amplifiers ROUT AVV1 V1 RIN V2 Unilateral amplifier in terms of “amplifier” parameters 1 y21 1 R A ROUT IN V y y11 y22 22 Review from Previous Lecture Relationship with Dependent Sources ? I1 I2 RIN ROUT AVRV2 V1 AVV1 V2 Two Port (Thevenin) Dependent sources from EE 201 200VB 16IA VIN IA VB Example showing two dependent sources Review from Previous Lecture Relationship with Dependent Sources ? I1 I2 RIN ROUT AVRV2 V1 AVV1 V2 Two Port (Thevenin) Dependent sources from EE 201 Voltage Transconductance Amplifier Vs=µVx Is=αVx Amplifier Voltage Dependent Voltage Dependent Voltage Source Current Source Transresistance Current Amplifier Vs=ρIx Is=βIx Amplifier Current Dependent Current Dependent Voltage Source Current Source Review From Previous Lecture Relationship with Dependent Sources ? I1 I2 RIN ROUT AVRV2 V1 AVV1 V2 Two Port (Thevenin) It follows that AVR=0 RIN= AV=µ ROUT=0 I1 I2 Vs=µVx V1 AVV1 V2 Two Port (Thevenin) V2=AVV1 Voltage dependent voltage source is a unilateral floating two-port voltage amplifier with RIN=∞ and ROUT=0 Review From Previous Lecture Relationship with Dependent Sources ? I1 I2 RIN ROUT AVRV2 V1 AVV1 V2 Two Port (Thevenin) It follows that AVR=0 RIN=0 ρ =RT ROUT=0 I1 I2 Vs=ρIx V1 RTI1 V2 Two Port (Thevenin) V2=RTI1 Current dependent voltage source is a unilateral floating two-port transresistance amplifier with RIN=0 and ROUT=0 Review From Previous Lecture Relationship with Dependent Sources ? I1 I2 RIN ROUT AVRV2 V1 AVV1 V2 Two Port (Thevenin) It follows that I1 I2 AII1 V V Is=βIx 1 2 Two Port (Thevenin/Norton) I2=AII1 Current dependent current source is a floating unilateral two-port current amplifier with RIN=0 and ROUT=∞ Review From Previous Lecture Relationship with Dependent Sources ? I1 I2 RIN ROUT AVRV2 V1 AVV1 V2 Two Port (Thevenin) It follows that I1 I2 GTI1 V V Is=αVx 1 2 Two Port (Thevenin/Norton) I2=GTV1 Voltage dependent current source is a floating unilateral two-port transconductance amplifier with RIN=∞ and ROUT=∞ Review From Previous Lecture Dependent Sources Dependent sources are unilateral two-port amplifiers with ideal input and output impedances Dependent sources do not exist as basic circuit elements but amplifiers can be designed to perform approximately like a dependent source • Practical dependentVs=µV xsources typicallyI sare=αV notx floating on input or output • One terminal is usually grounded • Input and output impedances of realistic structures are usually not ideal Why were “dependentVs= sources”ρIx introduced asIs= basicβIx circuit elements instead of two-port amplifiers in the basic circuits courses??? Why was the concept of “dependent sources” not discussed in the basic electronics courses??? Basic Amplifier Structures • MOS and Bipolar Transistors both have 3 primary terminals • MOS transistor has a fourth terminal that is generally considered a parasitic D terminal C G B B S E D C G B E S Transistors as 3-terminal Devices D C G B S E Small Signal Transistor Models as 3-terminal Devices Basic Amplifier Structures Observation: VOUT VOUT M1 R1 R VIN VIN These circuits considered previously have a terminal (emitter or source) common to the input and output in the small-signal equivalent circuit For BJT, E is common, input on B, output on C Termed “Common Emitter” For MOSFET, S is common, input on G, output on D Termed “Common Source” Basic Amplifier Structures Amplifiers using these devices generally have one terminal common and use remaining terminals as input and output Since devices are nearly unilateral, designation of input and output terminals is uniquely determined Three different ways to designate the common terminal D C Source or Emitter termed Common Source or Common Emitter G B Gate or Base termed Common Gate or Common Base S E Small Signal Transistor Models Drain or Collector as 3-termtermedinal Devices Common Drain or Common Collector Basic Amplifier Structures MOS BJT Common Input Output Common Input Output Common Source or Common Emitter S G D E B C Common Gate or Common Base G S D B E C Common Drain or Common Collector D G S C B E D C Identification of GInput and OutputB Terminals is not arbitrary S E It will be shown that all 3Sm aofll Sig ntheal Trans isbasictor Models amplifiers are useful ! as 3-terminal Devices Basic Amplifier Structures Common Source or Common Emitter Common Gate or Common Base Common Drain or Common Collector Objectives in Study of Basic Amplifier Structures 1. Obtain key properties of each basic amplifier 2. Develop method of designing amplifiers with specific characteristics using basic amplifier structures RC D Common Gate C Common Source Common Emitter inc RC INPUT G B OUTPUT Common Base Common Drain S Common CollectorE Small Signal Transistor Models Overallas Amplifier 3-termin aStruturel Devices Characterization of Basic Amplifier Structures D C G B S E Small Signal Transistor Models as 3-terminal Devices • Observe that the small-signal equivalent of any 3-terminal network is a two-port • Thus to characterize any of the 3 basic amplifier structures, it suffices to determine the two-port equivalent network • Since small signal model when expressed in terms of small-signal parameters of BJT and MOSFET differ only in the presence/absence of gπ term, can analyze the BJT structures and then obtain characteristics of corresponding MOS structure by setting gπ=0 C D G D B C G gπ gO gO VBE B VGS gmVBE gmVGS S E S E The three basic amplifier types for both MOS and bipolar processes Common Emitter Common Source Common Base Common Gate Common Collector Common Drain Will focus on the performance of the bipolar structures and then obtain performance of the MOS structures by observation The three basic amplifier types for both MOS and bipolar processes VOUT vOUT g mRL v be Vin g vv RL Vin π RL IN be Vbe gmVbe VOUT vOUT ARVL gm Common Emitter vIN VOUT VOUT vOUT g mRL v be gπ RL Vbe gmVbe vvIN be Vin RL vOUT Vin ARVLgm vIN Common Base VOUT vOUT g m g v beRL v v g g v R Vin gπ IN be m be L Vbe gmVbe Vin RL VOUT vOUT ggm RL RL A V 1 vIN1 g m g RL Common Collector • Significantly different gain characteristics for the three basic amplifiers • There are other significant differences too (RIN, ROUT, …) as well The three basic amplifier types for both MOS and bipolar processes Vin RL VOUT Common Emitter Common Source Common Emitter VOUT Vin RL Common Base Common Gate Common Base More general models are needed to accommodate biasing, understand performance capabilities,VOUT and include effects of loading of the basic structures Vin ComRmLon Collector Common Drain Two-port models are useful for characterizing the basic amplifier structures How canComm othen Co lletwoctor -port parameters be obtained for these or any other linear two-port networks? Two-Port Models of Basic Amplifiers widely used for Analysis and Design of Amplifier Circuits Methods of Obtaining Amplifier Two-Port Network i1 i2 Rin Ro V1 V2 AvRV 2 Av0V 1 1. VTEST : iTEST Method (considered in a previous lecture) 2. Write V1 : V2 equations in standard form Vi 1 = 1R IN + AVRV 2 V 2 = i 2R O + A V0 V 1 3. Thevenin-Norton Transformations 4. Ad Hoc Approaches Any of these methods can be used to obtain the two-port model Vi test: test Method for Obtaining Two-Port Amplifier Parameters SUMMARY from PREVIOUS LECTURE i1 i2 V Rin Ro out-test Vout-test AV0 Vtest V1 V2 AvRV 2 Av0V 1 V test If Unilateral A A Unilateral If i i TEST i1 2 V test R Rin in Ro i Vtest V1 V2 test VR =0 i i1 i2 TEST V R test R 0 in Ro i test V1 V2 Vtest AvRV 2 Av0V 1 i1 i2 V out-test R AVR in Ro V Vout-test V1 Vtest test A V V2 AvRV 2 v0 1 Will now develop two-port model for each of the three basic amplifiers and look at one widely used application of each Common Emitter Common Source Common Base Common Gate Common Collector Common Drain Consider Common Emitter/Common Source Two-port Models Common Emitter Common Source Common Base Common Gate Common Collector Common Drain Will focus on Bipolar Circuit since MOS counterpart is a special case obtained by setting gπ=0 Basic CE/CS Amplifier Structures VOUT VOUT R1 M1 R VIN VIN Common Emitter Amplifier Common Source Amplifier V OUT VOUT M1 R R1 VIN VIN Common Source Amplifier Common Emitter Amplifier Can include or exclude R and R1 in two-port models (of course they are different circuits) The CE and CS amplifiers are themselves two-ports ! Two-port model for Common Emitter Configuration B C gπ g Vbe O Common Emitter gmVbe E ? i1 i2 Ro Rin A V V1 v0 1 V2 {Ri, AV0 and R0} Two-Port Models of Basic Amplifiers widely used for Analysis and Design of Amplifier Circuits Methods of Obtaining Amplifier Two-Port Network i1 i2 Rin Ro V1 V2 AvRV 2 Av0V 1 1. VTEST : iTEST Method 2. Write V1 : V2 equations in standard form Vi 1 = 1R IN + AVRV 2 V 2 = i 2R O + A V0 V 1 3.
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