Lecture 19 - MIT
Spring 2007Lecture 191Lecture 19Transistor Amplifiers (I)Common-Source AmplifierOutline Amplifier fundamentals Common-source amplifier Common-source amplifier with current-source supplyReading Assignment:Howe and Sodini; Chapter 8, Sections :Quiz #2:April 25, 7:30-9:30 PM at Walker. Calculator Required. Open book. Spring 2007Lecture 192Amplifier Fundamentals Source resistance RSis associated onlywith small signal sources Choose ID= ISUP---> DC output current IOUT= 0 VOUT= 0+ + vsisRSvIN = VBIAS + vs iIN = IBIAS + is VBIASIBIASRSVoltage InputCurrent InputSupplyCurrent ISUPInputsourcesIntrinsicAmplifierActive DeviceiD = f(input) ISUPRLiOUT = idiD+ V V+ Spring 2007Lecture 1932. Common-Source Amplifier: VBIAS, RDand W/L of MOSFET selected to bias transistor in saturation and obtain desired output bias point ( VOUT= 0).Consider the following circuit: Consider intrinsic voltage amplifier - no loading RS= 0 RL---> VGS= VBIAS-VSSWatch notation: vOUT(t)=VOUT+vout(t)vsVBIASvOUTV+=VDDV-= VSSiRiDRDRSRLsignal source+ Spring 2007Lecture 194 Bias point calculation; Limits to signal swing Small-signal gain ; Frequency response [in a few days] Want:Transfer characteristics of amplifier:Load line view of amplifier:VOUTVGG-VSS0VDD-VSSVTVDDVSSVOU TVGG-VSS=VDD-VSSVGG-VSSVGG-VSS=VT0IR=IDV SSVDDVDD-VSSRDload lineVBIAS-Vss= VDD-VSSVBIAS-VssVBIAS-Vss= Spring 2007Lecture 195Bias point: choice of VBIAS, W/L, and RDto keep transistor
=VSS iR iD RD RS RL signal source +-signal load. 6.012 Spring 2007 Lecture 19 4 • Bias point calculation; • Limits to signal swing • Small-signal gain; • Frequency response [in a few days] Want: Transfer characteristics of amplifier: Load line view of amplifier: VOUT 0 T DD-VSSV GG-VSS VDD VSS VOUT VGG-VSS=VDD-VSS
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