Electronics Technology Fundamentals Operational Amplifiers OpAmp n Opamp

Electronics Technology Fundamentals Operational Amplifiers

Op-Amp. n Op-amp – เปนอปกรณขยายไฟตรงแบบอตราขยายสง (high-gain dc amplifier) โดยทม high input impedance และ low output impedance Two inputs: Inverting (-) และ noninverting (+) n Two dc power supply inputs: +V และ -V n Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 2 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Operational Amplifiers Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 3 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Operational Amplifiers n Op-Amp Supply Voltages Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 4 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Operational Amplifiers n IC Identification – many op-amps are identified using a seven-digit code n n n Prefix – บอกถงบรษททผลต Designator – ระบประเภทของ op-amp และมตวอกษร ตวระบถง operating temperature range Suffix – บอกถงชนดของ package Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 5 1 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Operational Amplifier n IC Identification (Continued) Manufacturer Codes Prefix Manufacturer AD/OP CA/HA KA LM MC NE/SE OPA RC/RM SG TI Analog Devices Harris Fairchild National Semiconductor ON Semiconductor Signetics Burr-Brown Raytheon Silicon General Texas Instruments Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell Temperature Codes Code Range ( C) C I M 0 to 70 -25 to 85 -55 to 125 C = Commercial I = Industrial M = Military 6 Package Codes Suffix D, VD J N, P, VP DM Package SMP Ceramic DIP Plastic DIP Micro SMP = Surface mount package DIP = Dual in-line package © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Operational Amplifiers n Op-Amp Packages n n n Metal Cans Dual-In-Line Packages (DIPs) Surface Mount Packages (SMPs) Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 7 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Operation Overview n Differential Amplifier n n The input stage of an op-amp A circuit that amplifies the difference of potential across the input terminals (Vdiff) Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 8 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Operation Overview n Differential Amplifier (Continued) where Vdiff = the voltage that will be amplified V 2 = the input voltage applied to the noninverting input V 1 = the input voltage applied to the inverting input Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 9 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Operation Overview n Op-Amp Gain n Open-Loop Gain (AOL) – the maximum possible gain provided by a given op-amp Usually greater than 10, 000 n Example: KA 741 – typical AOL = 200, 000 n Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 10 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Operation Overview n Op-Amp Gain (Continued) n Op-amp circuits usually contain a feedback path – reduces effective gain Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 11 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Operation Overview n Input/Output Polarity n n n ถาขา noninverting (+) มศกยเปนบวกมากกวา output จะเปน +V ถาขา inverting (-) มศกยเปนบวกมากกวา output จะเปน –V วธการคำนวณเพอหาขวของ op-amp output voltage: Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 12 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Operation Overview n Input/Output Polarity (Continued) Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 13 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Operation Overview n Supply Voltages – ระบถงขดจำกดของแรงดน output n n Circuit (a) – output ideally can go from +5 V to -5 V Circuit (b) – output ideally can go from 0 V to +5 V Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 14 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

Operation Overview n Supply Voltages (Continued) n ในทางปฏบต peak voltage จะมคาไมถงทง หรอ -V เนองจากแรงดนบางสวนจะตกครอมท output circuit Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 15 +V op-amp © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 3 Differential Amplifiers and Op-Amp Specifications – P 1 n The Basic Differential Amplifier – a circuit that produces an output that is proportional to the difference of two inputs Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell Insert Figure 22. 13 16 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 3 Differential Amplifiers and Op-Amp Specifications – P 2 n The Basic Differential Amplifier (Continued) Insert Figure 22. 14 Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 17 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 3 Differential Amplifiers and Op-Amp Specifications – P 3 n Modes of Operation n Single-Ended Mode – a signal is applied to only one input Differential Mode – two signals are applied Common Mode n n Identical signals are applied to both inputs Ideally the circuit output equals 0 V. The benefit of this mode is that any noise or undesired signal appearing at the two input simultaneously does not generate an output. Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 18 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 3 Differential Amplifiers and Op-Amp Specifications – P 4 n Output Offset Voltage n n A positive or negative voltage that appears at the output of an op-amp when no signal is applied to the inputs Due to an imbalance in VBE between the transistors in the differential amplifier Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 19 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 3 Differential Amplifiers and Op-Amp Specifications – P 5 n Output Offset Voltage (Continued) – can be eliminated by using the op-amp’s offset null pins Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 20 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 3 Differential Amplifiers and Op-Amp Specifications – P 6 n Input Offset Current n n A slight difference between the two input currents (i 1 and i 2) caused by a mismatch between the transistors Can also result in an output offset voltage Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 21 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 3 Differential Amplifiers and Op-Amp Specifications – P 7 n Input Offset Current (Continued) - a compensating resistor (RC) can be used to compensate for any current mismatch Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 22 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 3 Differential Amplifiers and Op-Amp Specifications – P 8 n Input Bias Current n n Inputs to an op-amp require some amount of dc biasing An op-amp will not product the expected output if either input is open Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 23 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 3 Differential Amplifiers and Op-Amp Specifications – P 9 n Common-Mode Rejection Ratio (CMRR) n n n Common-mode signals – identical signals that are applied simultaneously to the two inputs of an op-amp CMRR – a measure of the ability of an op-amp to “ignore” common-mode signals Technical Definition: CMRR is the ratio of differential voltage gain to common-mode voltage gain Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 24 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 3 Differential Amplifiers and Op-Amp Specifications – P 10 n Power Supply Rejection Ratio (PSRR) n n An op-amp rating that indicates the change in output voltage that occurs as a result of a change in supply voltage Example: The KA 741 has a PSRR of 77 d. B (minimum) Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 25 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 3 Differential Amplifiers and Op-Amp Specifications – P 11 n Output Short-Circuit Current n n Maximum value of output current as measured with the load shorted Example: The KA 741 has a output short-circuit current rating of 25 m. A Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 26 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 3 Differential Amplifiers and Op-Amp Specifications – P 12 n Slew Rate n n n A measure of how fast the output can change in response to a change at either signal input Example: The slew rate of the KA 741 is 0. 5 V/ S Maximum operating frequency: where Vpk = the peak output voltage from the op-amp Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 27 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 3 Differential Amplifiers and Op-Amp Specifications – P 13 n Slew Rate (Continued) – slew-rate distortion occurs when the input waveform is changing at a rate that is greater than that at which the opamp output can change Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 28 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 3 Differential Amplifiers and Op-Amp Specifications – P 14 n Input/Output Resistance n n Op-amps typically have high input resistance and low output resistance Example: KA 741 n n Input Resistance – 2 M (typical) Output Resistance – 75 up to 100 k. Hz, increases to approximately 300 at 1 MHz Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 29 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 3 Differential Amplifiers and Op-Amp Specifications – P 15 n Other Op-Amp Characteristics n n Input Voltage Range – the maximum differential input to the op-amp Large-Signal Voltage Gain – another name for open -loop voltage gain (AOL) Supply Current Rating – the quiescent current that is drawn from the power supply Power Consumption Rating – the amount of power that the op-amp will dissipate in its quiescent state Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 30 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 4 Inverting Amplifiers – P 1 n Inverting Amplifier – the op-amp counterpart of the common-emitter and common-source amplifiers Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 31 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 4 Inverting Amplifiers – P 2 n Virtual Ground Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 32 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 4 Inverting Amplifiers – P 3 n Closed-Loop Voltage Gain (ACL) – resulting voltage gain when a feedback path is present Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 33 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 4 Inverting Amplifiers – P 4 n Amplifier Input Impedance Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 34 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 4 Inverting Amplifiers – P 5 n Amplifier Output Impedance – since Rf is normally much greater than Zout for the op-amp, the output impedance of the circuit is usually assumed to be slightly less than the Zout rating of the op-amp, which is typically less than 100 Insert Figure 22. 19 Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 35 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 4 Inverting Amplifiers – P 6 n Amplifier CMMR where ACL = the closed-loop voltage gain of the inverting amplifier ACM = the common-mode gain of the op-amp Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 36 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 5 Noninverting Amplifiers – P 1 n Noninverting Amplifier n n Has much higher circuit input impedance than the inverting amplifier Does not produce a 180° phase shift Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 37 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 5 Noninverting Amplifiers – P 2 n Closed-Loop Voltage Gain (ACL) Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 38 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 5 Noninverting Amplifiers – P 3 n n n Amplifier Input Impedance – since the input signal is applied directly to the op-amp, the noninverting amplifier has extremely high input impedance Amplifier Output Impedance – slightly less than that of the op-amp Typical Values: Zin > 1 M and Zout < 100 Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 39 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 5 Noninverting Amplifiers – P 4 Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 40 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 5 Noninverting Amplifiers – P 5 n The Voltage Follower Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 41 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 6 Op-Amp Frequency Response – P 1 n Frequency Versus Gain n dc Amplifier – no lower cutoff frequency Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 42 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 6 Op-Amp Frequency Response – P 2 n Frequency Versus Gain (Continued) n n n Decreasing the voltage gain of an op-amp increases its maximum operating frequency Unity-Gain Frequency (funity) – the maximum operating frequency of an op-amp is measured at ACL = 0 d. B Gain-Bandwidth Trade. Off Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 43 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 6 Op-Amp Frequency Response – P 3 n Gain-Bandwidth Product – always equals the unity-gain frequency of the op-amp Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 44 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 7 Op-Amp Circuits – P 1 n Comparator – an op-amp circuit that compares two voltages and provides an output indicating the relationship between them Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 45 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 7 Op-Amp Circuits – P 2 n Comparator (Continued) Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 46 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 7 Op-Amp Circuits – P 3 n Comparator (Continued) n n Voltage divider used to set reference voltage Bypass capacitor prevents input signal variations from being coupled to the voltage-divider circuit through the op-amp Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 47 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 7 Op-Amp Circuits – P 4 n Comparator (Continued) - Circuit Variations Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 48 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 7 Op-Amp Circuits – P 5 n Integrator – a circuit that converts a square wave into a triangular wave Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 49 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 7 Op-Amp Circuits – P 6 n Integrator (Continued) where A = the area of the waveform V = the peak voltage of the waveform t = the pulse width of the waveform Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 50 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 7 Op-Amp Circuits – P 7 n Integrator (Continued) Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 51 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 7 Op-Amp Circuits – P 8 n Integrator (Continued) n Integrator Operation – for this simple circuit, the output is not linear because the capacitor does not charge/discharge at a linear rate Insert Figure 22. 33 Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 52 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 7 Op-Amp Circuits – P 9 n Integrator (Continued) n Integrator Operation (Continued) – op-amp provides constant-current capacitor charge producing a linear output, I 1 = Vin/R 1 Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 53 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 7 Op-Amp Circuits – P 10 n Differentiator – a circuit that provides an output that is proportional to the rate of change of its input signal Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 54 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 7 Op-Amp Circuits – P 11 n Summing Amplifier – an op-amp circuit that provides an output proportional to the sum of its inputs Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 55 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 7 Op-Amp Circuits – P 12 n A Summing Amplifier Application - Digital-to -Analog Converter Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 56 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 7 Op-Amp Circuits – P 13 n Summing Amplifier Modifications n Averaging Amplifier – a circuit that produces an output equal to the average of its inputs Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 57 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 7 Op-Amp Circuits – P 14 Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 58 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 7 Op-Amp Circuits – P 15 n Difference Amplifiers – provides an output that is proportional to the difference between its input voltages Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 59 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.

22. 7 Op-Amp Circuits – P 16 n Instrumentation Amplifiers – high-gain, high-CMRR circuit that is used to detect and amplify low-level signals Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell 60 © 2009 Pearson Higher Education, Upper Saddle River, NJ 07458. • All Rights Reserved.