1、Mix-signal MOS DesignComing ChenmgOUTRggCJCHigh SpeedGain StageDynamic RangeMatchingFET&LPNPmatchingCapmatchingResistormatchingThermal noise or NF&1/f noiseLinearityHarmonic DistortionggCmgAdvanced CMOSAnalog DesignV/L BJT1nDIMixed Signal Technology ConcernDevice Characteristics for Analog/RFqAnalog
2、:High Gm/ID ratio for Lower power But,CMOS has lower ratio.High Early Voltage(VA)for higher gain Deep submicron CMOS suffers lower VA.Good Linearity and low noise:Dynamic range and signal purity CMOS is good.Good matching:CMOS has VT and area mismatch issues(BJT is better).Low temperature linearity:
3、BJT is needed for zero-temperature bias circuitry.qRF:Low Noise Figure and:Dynamic range and signal purity in radio frequency.CMOS has higher NF(GaAs has better NF)and Low 1/f noise:important for narrow band application.CMOS has worse 1/f noise among different device technologies.Low Gate/base resis
4、tance:In deep sub-micron CMOS,gate resistance limited the width of transistor.Together with edge parasitics concern,combination of device width and total fingers has to consider all the different specification.Low Power:Good Substrate Isolation:Crosstalk suppression and high-Q on-chip components III
5、-V and SOS CMOS can provide insulating substrate.Deep N-well.Requirements for Analog MM/RF 3.3V FET are more widely used than core devices.Gm/ID ratio and Gm:Drivability.VA early voltage:Transistor Intrinsic Gain lower power consumption.Cgg and Junction Cap:Smaller capacitance results in higher spee
6、d and better stability.FET matching:Offset voltage(trade-off with chip area)Need detailed Vgs matching at operation range instead of VT matching Nitrided Gate Oxide(compared to Pure Oxide):It has smaller low-field mobility(mn)smaller mn at lower VGT.Much higher 1/f noise,impacting on voice band,RF b
7、and,direct-conversion.Parasitic Bipolar Transistor:3,good VBE matching,lower 2kT current.Vertical PNP can be good for PTAT and Bandgap reference.High-performance Lateral PNPNoise Figure(NF)Device Technology ComparisonqCMOS:VTH mismatch,higher 1/f noise,and lower Gm/ID ratio(drivability).Good lineari
8、ty,low cost,suitable for low voltage application.qSOI CMOS:worst VTH mismatch,much higher low-frequency noise.(compared to CMOS):higher wafer cost,and floating body effect.Lower junction capacitance and free of body effect for high speed/low power applications.qBJT and SiGe HBT in BiCMOS:Expensive p
9、rocess,limited for low voltage application(limited by VBE).Con:Higher Gm/ID ratio,Higher FT and Fmax,especially for SiGe for high speed SONET application.Lower 1/f noise(10 to 100 x smaller than CMOS),Good matching property.Passive Device for Analog MM/RF Precision Capacitor,1.3s Matching,2.Linearit
10、y(VCC),3.Precision(range),4.Density(fF/um2).VMIM and MOSCAP and LMIM Cap support.Precision Resistor,1.3s Matching,2.Temperature Coeff.(TCR)and VCR,3.Precision(range),4.Sheet Rho(W/1).Unsalicide Poly resistor and Spice model.On-chip Inductor,1.Q,density and fSR,2.3s Matching(for differential pair loa
11、ding),3.Coupling.For high Q,current effort is to reduce Rs.How about substrate loss?special ground plane or low-K!Design Kit:Impact of inductor thickness,metal width and spacing on Q,density and fSR.Cover from 900MHz to 4GHz.Varactor,1.Tuning range.2.Q.3.Density.N-MOSCAP and P+/N junction Varactors.
12、Passive device-ResistorqPerformance requirements:Sheet Rho and Range.Range can be improved by process optimization.3s matching.(3s 0.5%for an area of 100um2)Unsalicided P+poly resistor has better matching than N+polys.VCR and TCR.TCR is more important and it depends on implant species and dose.qResi
13、stor Family:Unsalicided P+poly resistor.Add an Salicide block mask(free).The normal rho is 300W,and range +/-15%.3s matching 0.5%and TCR 3000ppm/C).Unsalicide poly P-resistor can replace it with an extra Mask cost increase and much higher TCR.Passive Device-CapacitorqPerformance requirements:Precisi
14、on:Capacitance and Range.Density:high density capacitor save chip area.Cap matching and VCC1:Good matching save chip area.Substrate loss and Q:stray capacitance can increase signal loss.qCapacitor Family:Metal-Insulator-Metal Capacitor(VMIM):needs intra-metal layer and one extra mask.Good 3s matchin
15、g(0.25%for a value of 0.5pF),good TCC1 and VCC1(1fF/um2)Free for digital process with lower TCC1 and VCC1 than VMIMs,but mismatch is higher than VMIMs.Q is high due to narrow metal spacing(3 and good ideality(less 2kT current)in the operating range(0.5V to 0.7V).25x25 VBJTVB=0,VC=-1V(VCB=-1V),Sweep
16、VE from 0.2 to 1V1.E-121.E-111.E-101.E-091.E-081.E-071.E-061.E-051.E-041.E-031.E-020.30.40.50.60.70.80.91VEB(V)IC,IB(A)0.00.51.01.52.02.53.03.54.04.55.0HFEICIB1KT currentHFEM1M2M3M4Q1Q2Q3R1R2AnAPTATCurrentVREFPTAT or Bandgap Reference1)ln(RnVITPTAT)ln(123nVRRVVTBEREFGate-Controlled Lateral PNP BJT Common Base Configuration VB=0V,VG=-0.4V 0.4V PMOS off and LPNP on VG 0.4V Belta 100 PMOS on and LNPNP off VG 0.4V and VE 0.6V Belta is modulated by VG Both PMOS and LPNP on VG 0.6V Belta smaller
