ECE/CS 5780/6780: Embedded System DesignChris J. MyersLecture 17: Operational AmplifiersChris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design1 / 29Introduction to Analog InterfacingMost embedded systems include components that measure and/orcontrol real-world parameters.These include position, speed, temperature, etc.Usually exist in a continuous, or analog, form.Often need to amplify, filter, and convert these signals to digital form.This chapter develops analog circuit building blocks for data acquisitionand control systems.Chris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design2 / 29Ideal Op AmpsVout= K(Vy−Vx)1Voltage ranges are bounded by the supply voltages, ±Vs.2Input currents, Ixand Iy, are zero.3Negative feedback drives Vxto equal Vy.4Positive feedback or no feedback drives Voutto equal −Vsor +Vs.Chris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design3 / 29Various Op AmpsOp amp Description Open loop gain ±Vs±IsOPA4227 High Precision 160 dB ±5 to ±15 V ±3.8 mAOPA4132 High-Speed FET 130 dB ±2.5 to ±18 V ±4.8 mATLC2274 Rail-to-Rail 104 dB 0 to 5 or ±5 V 3 mAChris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design4 / 29Input ImpedanceOp amp RcmRdiffOPA4227 1 GΩ 10 MΩOPA4132 1013Ω 1013ΩTLC2274 1012Ω 1012ΩChris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design5 / 29Output ImpedanceChris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design6 / 29Offset Voltage, Offset Current, and Bias CurrentOp amp VosIosIbOPA4227 0.075 mV 10 nA 10 nAOPA4132 0.5 mV 50 pA 50 pATLC2274 3 mV 100 pA 100 pAChris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design7 / 29Noise DensityOp amp enOPA4227 3 nV/√HzOPA4132 23 nV/√HzTLC2274 50 nV/√HzChris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design8 / 29Transient ResponseOp amp dV/dt, Slew rateOPA4227 2.3 V/µsOPA4132 20 V/µsTLC2274 3.6 V/µsChris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design9 / 29Frequency ResponseOp amp f1OPA4227 8 MHzOPA4132 8 kHzTLC2274 2.18 MHzChris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design10 / 29Power Gain (Adb)Combines voltage gain, input impedance, and output impedance.Pin=V2inRinPout=V2outRoutAdb= 10log10PoutPin= 20log10VoutVin+ 10log10RinRoutChris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design11 / 29Threshold DetectorChris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design12 / 29Simple Rules for Linear Op Amp CircuitsChoose quality components.Negative feedback required to create linear mode circuit.Assume no current flows into the op amp inputs.Assume negative feedback equalizes input voltages.Choose resistor values in the 1kΩ to 1MΩ range.BW depends on the gain and the op amp performance.Chris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design13 / 29Simple Rules for Linear Op Amp Circuits (cont)Equalize the effective resistance to ground at the two op amp inputs.Input impedance is input voltage / input current.Chris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design14 / 29Simple Rules for Linear Op Amp Circuits (cont)Match input impedances to improve common-mode rejection ratio(CMRR).Chris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design15 / 29Inverting AmplifierChris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design16 / 29Inverting Amplifier with -2.5V to 2.5V RangeChris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design17 / 29Noninverting AmplifierChris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design18 / 29Model for Linear Circuit DesignVout= A1V1+ A2V2+ ...+AnVn+ BChris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design19 / 29Linear Circuit DesignVout= 5V1−3V2+ 2V3−10Choose a reference voltage from available reference voltage chips.Vref= 5VRewrite the design equation in terms of the reference voltage, Vref.Vout= 5V1−3V2+ 2V3−2VrefAdd a ground input to the equation such that the sum of the gains is 1.Vout= 5V1−3V2+ 2V3−2Vref−VgChoose a feedback resistor, Rf, in range of 10 kΩ to 1 MΩ.Rf= 150kΩ R1= 30kΩ R2= 50kΩR3= 75kΩ Rref= 75kΩ Rg= 150kΩBuild the circuit: connect positive gain inputs to positive terminal andnegative gain inputs to the negative terminal.Chris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design20 / 29Linear Op Amp CircuitChris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design21 / 29Instrumentation AmplifierChris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design22 / 29Current-to-Voltage CircuitChris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design23 / 29Voltage-to-Current CircuitChris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design24 / 29Integrator CircuitChris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design25 / 29Derivative CircuitChris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design26 / 29HysteresisChris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design27 / 29Voltage Comparators with HysteresisChris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design28 / 29Analog IsolationChris J. Myers (Lecture 17: OpAmps)ECE/CS 5780/6780: Embedded System Design29 /
View Full Document
Unlocking...