John Brown Art Kay Tim Green Tina-TI

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High Current V-I Circuits. The Four Musketeers of HPL. Recognize. Analyze. Synthesize. Tina-ize. John Brown Art Kay Tim Green Tina-TI. Potential Applications, End Equipment, Markets Circuit Topologies Circuit Stability Issues - PowerPoint PPT Presentation

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<ul><li><p> John Brown Art Kay Tim Green Tina-TISynthesizeTina-izeThe Four Musketeers of HPLAnalyzeRecognizeHigh Current V-I Circuits</p></li><li><p>V-I Circuit Recognize ObjectivesPotential Applications, End Equipment, MarketsCircuit TopologiesCircuit Stability IssuesPower Dissipation IssuesTransient Protection IssuesPCB IssuesSemiconductor Overstress Issues</p></li><li><p>V-I Circuit Analyze, Synthesize, Tina-ize ObjectivesProvide Synthesis Techniques for Common TopologiesProvide Tools to Simplify Stability AnalysisProvide Analysis Techniques for Power DissipationProvide Solutions for Common Transient ProblemsProvide Tips for PCB LayoutsProvide Tricks for Tina-TI Analysis</p></li><li><p>Power Amplifiers Strategy for Markets1. High Volume GrowthCommunications Optical Networking ONET (TECs, Laser Diode Pumps, Avalanche Photodiode Bias HV)DLP Digital Light Projectors (high voltage OPA)Industrial Electromechanical (OPA, PWM)Automotive Electromechanical (OPA, PWM)2. Gen Std Catalog Products Steady Growth Industrial, Medical, Lab, ATE, Some Audio, ConsumerHigh Speed Buffers, High Voltage, High Current OPAs</p></li><li><p>Power Amplifiers Applications in Markets1. Test, Particularly Automated ATEAnalog Pin Driver, Power V &amp; I Excitation2. Power Line CommunicationHigh Pulse Current Drive Through Transformeror Capacitor Coupled ac Power Line (Residential &amp; Commercial)3. Displays High Current Driver for Dithering Projected Light Beam, High Voltage for Ink Jet Printers4. Industrial, Medical, Scientific, Analytical, and Laboratory TEC Drivers, Electromechanical Linear Valve/Positioner Drivers, Motors, Power Supplies5. Optical Networking / Gen Laser SystemsTEC Drivers (Thermo-electric Coolers), Laser Pumps 6. Some AudioHeadphone and Speaker Drivers7. Some AutomotivePower Steering Pumps, Window MotorsCOMPETITION1. Mostly Discrete2. National Semiconductor, ST, Maxim, Allegro, ON-SEMI, International Rectifier, Infineon, Toshiba</p></li><li><p>Review - Essential Principles Poles, Zeros, Bode Plots Op Amp Loop Gain Model Loop Gain Test and 1/ Rate-of-Closure Stability Criteria Loop Gain Rules-of-Thumb for Stability RO and ROUT</p></li><li><p>Commercial Break(Shameless Self-Promotion)See 15 Part Series: Operational Amplifier Stabilityhttp://www.analogzone.com/acqt0704.htm</p></li><li><p>Poles and Bode PlotsPole Location = fPMagnitude = -20dB/Decade SlopeSlope begins at fP and continues down as frequency increasesActual Function = -3dB down @ fPPhase = -45/Decade Slope through fPDecade Above fP Phase = -90Decade Below fP Phase = 0A(dB) = 20Log10(VOUT/VIN)</p><p>AC</p><p>R</p><p>C</p><p>VIN</p><p>VOUT</p><p>A = VOUT/VIN</p><p>Single Pole Circuit Equivalent</p><p>X100,000</p><p>0</p><p>20</p><p>40</p><p>60</p><p>80</p><p>100</p><p>10M</p><p>1M</p><p>100k</p><p>10k</p><p>1k</p><p>100</p><p>10</p><p>1</p><p>Frequency (Hz)</p><p>A (dB)</p><p>+90</p><p>-90</p><p>+45</p><p>+-45</p><p>10</p><p>100</p><p>1k</p><p>10k</p><p>100k</p><p>1M</p><p>10M</p><p>Frequency (Hz)</p><p>0</p><p>q</p><p>(degrees)</p><p>-20dB/Decade-6dB/Octave</p><p>-45o @ fP</p><p>-45o/Decade </p><p>fP</p><p>-90o</p><p>0o</p><p>G</p><p>0.707G = -3dB</p><p>Straight-Line Approximation</p><p>Actual Function</p></li><li><p>Zeros and Bode PlotsZero Location = fZMagnitude = +20dB/Decade SlopeSlope begins at fZ and continues up as frequency increasesActual Function = +3dB up @ fZPhase = +45/Decade Slope through fZDecade Above fZ Phase = +90Decade Below fZ Phase = 0A(dB) = 20Log10(VOUT/VIN)</p><p>AC</p><p>R</p><p>C</p><p>VOUT</p><p>A = VOUT/VIN</p><p>Single Zero Circuit Equivalent</p><p>X100,000</p><p>0</p><p>20</p><p>40</p><p>60</p><p>80</p><p>100</p><p>10M</p><p>1M</p><p>100k</p><p>10k</p><p>1k</p><p>100</p><p>10</p><p>1</p><p>Frequency (Hz)</p><p>A (dB)</p><p>+90</p><p>-90</p><p>+45</p><p>+-45</p><p>10</p><p>100</p><p>1k</p><p>10k</p><p>100k</p><p>1M</p><p>10M</p><p>Frequency (Hz)</p><p>0</p><p>q</p><p>(degrees)</p><p>+90o</p><p>0o</p><p>+45o/Decade </p><p>+45o @ fZ</p><p>fZ</p><p>+20dB/Decade+6dB/Octave</p><p>Straight-Line Approximation</p><p>G</p><p>1.414G = +3dB(1/0.707)G = +3dB</p><p>Actual Function</p></li><li><p>Op Amp: Intuitive Model</p><p>+</p><p>-</p><p>K(f)</p><p>VDIFF</p><p>IN+</p><p>IN-</p><p>RIN</p><p>RO</p><p>VO</p><p>VOUT</p><p>x1</p></li><li><p>Op Amp Loop Gain ModelVOUT/VIN = Acl = Aol/(1+Aol)If Aol &gt;&gt; 1 then Acl 1/Aol: Open Loop Gain: Feedback FactorAcl: Closed Loop Gain1/b = Small Signal AC Gainb = feedback attenuation</p><p>+</p><p>-</p><p>+</p><p>-</p><p>S</p><p>VOUT</p><p>b network</p><p>b</p><p>RF</p><p>RI</p><p>VIN</p><p>Aol</p><p>S</p><p>+</p><p>-</p><p>VOUT</p><p>VIN</p><p>VFB</p><p>VFB</p><p>RF</p><p>RI</p><p>b =VFB/VOUT</p><p>VOUT</p><p>b network</p></li><li><p>Stability Criteria</p></li><li><p>Traditional Loop Gain TestOp Amp Loop Gain ModelOp Amp is Closed LoopSPICE Loop Gain Test:Break the Closed Loop at VOUTGround VINInject AC Source, VX, into VOUTAol = VY/VX</p><p>+</p><p>-</p><p>+</p><p>-</p><p>b network</p><p>RF</p><p>RI</p><p>VIN</p><p>VFB</p><p>VOUT</p><p>+</p><p>-</p><p>+</p><p>-</p><p>RF</p><p>RI</p><p>VIN</p><p>b network</p><p>VFB</p><p>VOUT</p><p>VX</p><p>VY</p><p>1GF</p><p>1GH</p><p>Short for ACOpen for DC</p><p>Open for ACShort for DC</p></li><li><p> and 1/ is easy to calculate as feedback network around the Op Amp1/ is reciprocal of Easy Rules-Of-Thumb and Tricks to Plot 1/ on Op Amp Aol Curve </p><p>+</p><p>-</p><p>+</p><p>-</p><p>VOUT</p><p>b network</p><p>RF</p><p>RI</p><p>VIN</p><p>VFB</p><p>VFB</p><p>RF</p><p>RI</p><p>b =VFB/VOUT</p><p>VOUT</p><p>b network</p></li><li><p>Loop Gain Using Aol &amp; 1/Plot (in dB) 1/ on Op Amp Aol (in dB)Aol = Aol(dB) 1/(dB)Note how Aol changes with frequency</p><p>Proof (using log functions): 20Log10[Aol] = 20Log10(Aol) - 20Log10(1/) = 20Log10[Aol/(1/)] = 20Log10[Aol] </p><p>0</p><p>20</p><p>40</p><p>60</p><p>80</p><p>100</p><p>10M</p><p>1M</p><p>100k</p><p>10k</p><p>1k</p><p>100</p><p>10</p><p>1</p><p>Frequency (Hz)</p><p>Aol (dB)</p><p>fcl</p><p>1/b </p><p>Acl</p><p>Aol</p><p>Aol b(Loop Gain)</p><p>Closed Loop Response</p><p>Open Loop Response</p></li><li><p>Stability Criteria using 1/ &amp; AolAt fcl: Loop Gain (Aolb) = 1</p><p>Rate-of-Closure @ fcl =(Aol slope 1/ slope)*20dB/decade Rate-of-Closure @ fcl = STABLE**40dB/decade Rate-of-Closure@ fcl = UNSTABLE</p><p>0</p><p>20</p><p>40</p><p>60</p><p>80</p><p>100</p><p>10M</p><p>1M</p><p>100k</p><p>10k</p><p>1k</p><p>100</p><p>10</p><p>1</p><p>Frequency (Hz)</p><p>Aol (dB)</p><p>Aol</p><p>1/b1</p><p>1/b2</p><p>1/b3</p><p>1/b4</p><p>fcl1</p><p>fcl4</p><p>fcl3</p><p>fcl2</p><p>*</p><p>*</p><p>**</p><p>**</p></li><li>Loop Gain Bandwidth Rule: 45 degrees for f &lt; fclAol (Loop Gain) Phase PlotLoop Stability Criteria: </li><li><p>Poles &amp; Zeros Transfer: (1/, Aol) to Aol</p><p>Aol &amp; 1/ PlotLoop Gain Plot(Aol)To Plot Aol from Aol &amp; 1/ Plot:</p><p>Poles in Aol curve are poles in Aol (Loop Gain)PlotZeros in Aol curve are zeros in Aol (Loop Gain) Plot</p><p>Poles in 1/ curve are zeros in Aol (Loop Gain) PlotZeros in 1/ curve are poles in Aol (Loop Gain) Plot[Remember: is the reciprocal of 1/]</p><p>0</p><p>20</p><p>40</p><p>60</p><p>80</p><p>100</p><p>10M</p><p>1M</p><p>100k</p><p>10k</p><p>1k</p><p>100</p><p>10</p><p>1</p><p>Frequency (Hz)</p><p>A (dB)</p><p>Aol</p><p>fcl</p><p>1/b</p><p>fp1</p><p>fp2</p><p>fz1</p><p>Aol</p><p>b</p><p>0</p><p>20</p><p>40</p><p>60</p><p>80</p><p>100</p><p>10M</p><p>1M</p><p>100k</p><p>10k</p><p>1k</p><p>100</p><p>10</p><p>1</p><p>Frequency (Hz)</p><p>A (dB)</p><p>fp1</p><p>fz1</p><p>fp2</p><p>fcl</p></li><li><p>Frequency Decade Rules for Loop GainLoop Gain View: Poles: fp1, fp2, fz1; Zero: fp3</p><p>Rules of Thumb for Good Loop Stability:</p><p> Place fp3 within a decade of fz1 fp1 and fz1 = -135 phase shift at fz1 fp3 &lt; decade will keep phase from dipping further</p><p> Place fp3 at least a decade below fcl Allows Aol curve to shift to the left by one decade</p><p>+</p><p>-</p><p>+</p><p>-</p><p>VIN</p><p>RI</p><p>RF</p><p>VOUT</p><p>CL</p><p>Cn</p><p>Rn</p><p>0</p><p>20</p><p>40</p><p>60</p><p>80</p><p>100</p><p>10M</p><p>1M</p><p>100k</p><p>10k</p><p>1k</p><p>100</p><p>10</p><p>1</p><p>Frequency (Hz)</p><p>A (dB)</p><p>fcl</p><p>fp1</p><p>fp2</p><p>fz1</p><p>fp3</p><p>Aol</p><p>1/Beta</p><p>VOUT/VIN</p></li><li><p>Op Amp Model for Derivation of ROUT From: Frederiksen, Thomas M. Intuitive Operational Amplifiers. McGraw-Hill Book Company. New York. Revised Edition. 1988.ROUT = RO / (1+Aol)</p><p>+</p><p>-</p><p>RDIFF</p><p>xAol</p><p>RO</p><p>-IN</p><p>+IN</p><p>-</p><p>+</p><p>VE</p><p>Op Amp Model</p><p>1A</p><p>VOUT</p><p>VO</p><p>RF</p><p>RI</p><p>IOUT</p><p>VFB</p><p>ROUT = VOUT/IOUT</p></li><li><p>Op Amp Model for Loop Stability AnalysisRO is constant over the Op Amps bandwidth RO is defined as the Op Amps Open Loop Output Resistance RO is measured at IOUT = 0 Amps, f = 1MHz (use the unloaded RO for Loop Stability calculations since it will be the largest value worst case for Loop Stability analysis)RO is included when calculating b for Loop Stability analysis</p></li><li><p>RO &amp; Op Amp Output Operation Bipolar Power Op Amps CMOS Power Op Amps Light Load vs Heavy Load</p></li><li><p>RO Measure w/DC Operating Point: IOUT = 0mA</p></li><li><p>RO Measure w/DC Operating Point: IOUT = 0mARO = VOA / AM1RO = 9.61mVrms / 698.17Arms RO = 13.765</p></li><li><p>RO Measure w/DC Operating Point IOUT = 4.45mA Sink</p></li><li><p>RO Measure w/DC Operating Point IOUT = 4.45mA SinkRO = VOA / AM1RO = 3.45Vrms / 706.25Arms RO = 4.885</p></li><li><p>RO Measure w/DC Operating Point IOUT = 5.61mA Source</p></li><li><p>RO Measure w/DC Operating Point IOUT = 5.61mA SourceRO = VOA / AM1RO = 3.29mVrms / 700.98Arms RO = 4.693</p></li><li><p>RO Measure w/DC Operating Point IOUT = 2.74A Source</p></li><li><p>RO Measure w/DC Operating Point IOUT = 2.74A SourceRO = VOA / AM1RO = 314.31uVrms / 550.1Arms RO = 0.571</p></li><li><p>RO Measure w/DC Operating Point IOUT = 2.2A Sink</p></li><li><p>RO Measure w/DC Operating Point IOUT = 2.2A SinkRO = VOA / AM1RO = 169.92uVrms / 635.16Arms RO = 0.267</p></li><li><p>RO Measure w/DC Operating Point IOUT = 0A</p></li><li><p>RO Measure w/DC Operating PointIOUT = 0ARO = VOA / AM1RO = 4.42mVrms / 702.69Arms RO = 6.29</p></li><li><p>RO Measure w/DC Operating PointIOUT = 1A Sink</p></li><li><p>RO Measure w/DC Operating PointIOUT = 1A SinkRO = VOA / AM1RO = 166.76Vrms / 540.19Arms RO = 0.309</p></li><li><p>RO Measure w/DC Operating PointIOUT = 1A Source</p></li><li><p>RO Measure w/DC Operating PointIOUT = 1A SourceRO = VOA / AM1RO = 166.61Vrms / 540.34Arms RO = 0.308</p></li><li><p>Non-Inverting Floating Load V-I Basic TopologyStability Analysis (w/effects of Ro)1/b &amp; Aol TestLoop Gain TestTransient TestSmall Signal BW for Current Control</p></li><li><p>Non-Inverting V-I Floating LoadIOUT = VP / RSIOUT = {(R2*VIN) / (R1A + R1B + R2)} / RS+5V3.03A-5V-3.03AVPVPVPOp Amp Point of Feedback is VRSOp Amp Loop Gain forces +IN (VP) = -IN = VRS +1V-1V</p></li><li><p>Non-Inverting V-I Floating LoadRO Reflected Outside of Op Amp</p></li><li><p>Non-Inverting V-I Floating LoadFB#1 DC 1/b Derivation</p></li><li><p>Non-Inverting V-I Floating LoadFB#1 1/b Derivation</p></li><li><p>Non-Inverting V-I Floating LoadFB#1 1/b Data for RO No Load &amp; Full Load</p></li><li><p>OPA548 Data Sheet Aol</p></li><li><p>Non-Inverting V-I Floating LoadFB#1 1/b Plot for RO No Load &amp; Full Load</p></li><li><p>Non-Inverting V-I Floating LoadFB#1 1/b Tina SPICE</p></li><li><p>Non-Inverting V-I Floating LoadFB#1 1/b Tina SPICE Results</p></li><li><p>Non-Inverting V-I Floating LoadFB#1 1/b Tina SPICE Results</p></li><li><p>Non-Inverting V-I Floating LoadFB#1 Loop Gain Tina SPICE Results</p></li><li><p>Non-Inverting V-I Floating LoadFB#1 Transient Analysis Tina SPICE Circuit</p></li><li><p>Non-Inverting V-I Floating LoadFB#1 Transient Analysis Tina SPICE Results</p></li><li><p>Non-Inverting V-I Floating LoadAdd FB#2 and Predict 1/bNote: Load Current Control begins to roll-off in frequency where FB#2 dominates</p></li><li><p>Large Small Answer: The largest (smallest 1/) will dominate!How will the two feedbacks combine?</p><p>+</p><p>-</p></li><li><p>Non-Inverting V-I Floating LoadFB#2 Circuit</p></li><li><p>Non-Inverting V-I Floating LoadFB#2 High Frequency 1/b</p></li><li><p>Non-Inverting V-I Floating LoadFB#2 fz1</p></li><li><p>Non-Inverting V-I Floating LoadTina SPICE Loop Test</p></li><li><p>Non-Inverting V-I Floating LoadAol and 1/b Tina SPICE Results</p></li><li><p>Non-Inverting V-I Floating LoadLoop Gain Tina SPICE Results</p></li><li><p>Non-Inverting V-I Floating LoadIOUT/VIN AC Response Circuit</p></li><li><p>Non-Inverting V-I Floating LoadIOUT/VIN AC Tina SPICE Results</p></li><li><p>Non-Inverting V-I Floating LoadIOUT/VIN Transient Circuit</p></li><li><p>Non-Inverting V-I Floating LoadIOUT/VIN Transient Tina SPICE Results</p></li><li><p>Inverting V-I Floating LoadIOUT = {-VIN*(RF/RI)} / RSIOUT = -VIN*{RF/ (RI*RS)}+5V-3.03A-5V+3.03AOp Amp Point of Feedback is VRSOp Amp Loop Gain forces VRS = -VIN (RF/RI)-1V+1VStability Analysis &amp; Compensation Techniques similar to Non-Inverting V-I Floating Load</p></li><li><p> Grounded Load V-IImproved Howland Current Pump Basic TopologyStability Analysis (w/effects of Ro)1/b &amp; Aol TestLoop Gain TestTransient TestSmall Signal BW for Current Control</p></li><li><p>Improved Howland Current PumpIL Accuracy CircuitRT allows for trim to optimum ZOUT and improved DC Accuracy</p></li><li><p>Improved Howland Current PumpV-I DC Accuracy Calculations1% Resistors (w/RT=0) could yield only 9% Accuracy at T=25C</p><p>Still useful for V-I control in Motors/Valves V-Torque ControlOuter position feedback adjusts V for final position</p></li><li><p>Improved Howland Current PumpGeneral EquationSet RX=RF and RZ=RI</p></li><li><p>Improved Howland Current PumpSimplified Equation</p></li><li><p>Improved Howland AC AnalysisOp Amp sees differential [(-IN) (+IN)] feedbackb = b- - b+ (Must be positive number else oscillation!)RFRI</p></li><li><p>Improved Howland AC Analysis</p></li><li><p>Improved Howland AC AnalysisInclude Effects of RORFRI</p></li><li><p>Improved Howland b- Calculation</p></li><li><p>Improved Howland b+ Calculation</p></li><li><p>Improved Howland 1/b Calculation</p></li><li><p>Improved Howland b- CalculationRO = Full Load</p></li><li><p>Improved Howland b+ CalculationRO = Full Load</p></li><li><p>Improved Howland 1/b CalculationRO = Full Load</p></li><li><p>Improved Howland 1/b CalculationNo Load &amp; Full Load</p><p>Change in RO from No Load to Full Load has nosignificant impact on the 1/b Plot</p></li><li><p>OPA569 Data Sheet Aol</p></li><li><p>Improved Howland 1/b Plot - Full Load</p></li><li><p>Improved Howland 1/b Tina SPICE Plot - Full Load</p></li><li><p>Improved Howland Loop Gain Tina SPICE Plot - Full Load</p></li><li><p>Improved Howland Tina Transient Analysis CircuitRFRI</p></li><li><p>Improved Howland Tina Transient Analysis Results</p></li><li><p>Improved HowlandModified 1/b for Stability</p></li><li><p>b+ FB#2 Calculation to Modify 1/b for Stability</p></li><li><p>Improved Howland AC AnalysisFinal Design for StabilityRFRI</p></li><li><p>Improved Howland AC Analysis1/b - Final Design for Stabilityfcl</p></li><li><p>Improved Howland AC AnalysisLoop Gain - Final Design for Stabilityfcl</p></li><li><p>Improved Howland AC Transfer AnalysisIL/VIN - Final Design for StabilityRFRI</p></li><li><p>Improved Howland AC Transfer AnalysisIL/VIN - Final Design for Stability</p></li><li><p>Improved Howland Transient AnalysisIL/VIN - Final Design for StabilityRFRI</p></li><li><p>Improved Howland Transient AnalysisIL/VIN - Final Design for Stability</p></li><li><p>High Current V-I General ChecklistLarge Signal &amp; Transient SOA Considerations (V=L*di/dt)Bipolar Output Stages &amp; OscillationsHigh Current GroundingHigh Current PCB TracesHigh Current Supply IssuesPower Supply Bypass (Low f &amp; High f)Transient Protection (Supply, VIN, VOUT)Power Dissipation Considerations (see V-I Circuits Using External Transistors section)Consider:Short Circuit to Ground Power Dissipation Heatsink SelectionCurrent Sense Resistor (RS) Power Dissipation</p></li><li><p>V-I Large Signal Limits: V=Ldi/dt</p></li><li><p>Violate the Laws of Physics and Pay the Price!</p></li><li><p>Instant V-I Reversal SOA Violations</p></li><li><p>Output Stages fosc &gt; UGBW oscillates unloaded? -- no oscillates with VIN=0? -- noSome Op Amps use composite output stages, usually on the negative output, that contain local feedback paths. Under reactive loads these output stages can oscillate.The Output R-C Snubber Network lowers the high frequency gain of the output stage preventing unwanted oscillations under reactive loads.PROBLEMSOLUTION</p><p>-VS</p><p>LOAD</p><p>+</p><p>-</p><p>+</p><p>-</p><p>4.7kW</p><p>VIN</p><p>RF</p><p>RI</p><p>100kW</p><p>100kW</p><p>VOUT</p><p>RSN</p><p>CSN</p><p>10W to 100W</p><p>0.1mF to 1mF</p></li><li><p>Ground Loops fosc &lt; UGBW oscillates unloaded? -- no oscillates with VIN=0? -- yesGround loops are created from load current flowing through parasitic resistances. If part of VOUT is fed back to Op Amp +input, positive feedback and oscillations can occur.</p><p>Parasitic resistances can be made to look like a common mode input by using a Single-Point or Star ground connection. SOLUTIONPROBLEM</p><p>+</p><p>-</p><p>+</p><p>-</p><p>-VS</p><p>+VS</p><p>RL</p><p>RGy</p><p>RGx</p><p>RGv</p><p>RGw</p><p>RF</p><p>RI</p><p>Ground</p><p>IL</p><p>VIN</p><p>VOUT</p><p>+</p><p>-</p><p>+</p><p>-</p><p>RG</p><p>StarGround Point</p><p>VIN</p><p>VOUT</p><p>-VS</p><p>+VS</p><p>RL</p><p>RF</p><p>RI</p></li><li><p>PCB Traces fosc &lt; UGBW oscillates unloaded? -- may or may not oscillates with VIN=0? -- may or may notDO NOT route high current, low impedance output traces near high impedance input traces.DO route high current output traces adjacent to each other (on top of each other in a multi-layer PCB) to form a twisted pair for EMI cancellation.</p><p>+</p><p>-</p><p>+</p><p>-</p><p>VIN</p><p>VOUT</p><p>RI</p><p>RF</p><p>Rs</p><p>GND</p></li><li><p>Supply LinesLoad current, IL, flows through power supply resistance, Rs, due to PCB trace or wiring. Modulated supply voltages appear at Op Amp Power pins. Modulated signal couples into amplifier which relies on supply pins as AC Ground.Power supply lead inductance, Ls, interacts with a capacitive load, CL, to form an oscillatory LC, high Q, tank circuit. fosc &lt; UGBW oscillates unloaded? -- no oscillates with VIN=0? -- may or may notPROBLEMPROBLEM</p><p>GainStage</p><p>Power Stage</p><p>RL</p><p>IL</p><p>-vs</p><p>Rs</p><p>+</p><p>-</p><p>+vs</p><p>Ls</p><p>CL</p></li><li><p>Proper Supply Line DecoupleCLF: Low Frequency Bypass10F / Amp Out (peak) Aluminum Electrolytic or Tantalum&lt; 4 in (10cm) from Op Amp CHF: High Frequency Bypass0.1F Ceramic...</p></li></ul>

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