James Kelly Nathan Knight Gustavo Lee Operational Amplifiers

James Kelly Nathan Knight Gustavo Lee Operational Amplifiers

Presentation Outline � Introduction � Characteristics of Ideal and Real Op-Amps � Basic Circuits of Op-Amps � Applications � Exercise

What is an Op-Amp? � An Operational Amplifier (known as an “Op-Amp”) is an integrated circuit that sets an output voltage based on the input voltages provided. � In a circuit, it is used to perform an operation and an amplification where the operation may be add, subtract, filter, integrate, differentiate, etc. � Op-Amps are composed of transistors, resistors, capacitors, and diodes.

Brief History � 1941: Karl Swartzel of Bell Labs developed the first Op-Amp. Used 3 vacuum tubes, only one input (inverting), and operated on + 350 V to achieve 90 d. B gain. � 1947: Loebe Julie developed the Op-Amp as it is known today, with two inputs – inverting and non-inverting. The differential input made a whole range of new functionality possible. � 1953: First commercially available Op-Amp. George A. Philbrick Researches (GAP-R). GAP-R pioneered the first reasonable-cost, mass-produced operational amplifier � 1961: Advent of solid-state, discrete Op-Amps. Made possible by the invention of the silicon transistor, which led to the concept of Integrated Circuits (IC) Reduced power input to ± 15 V to ± 10 V � 1962: Op-Amp in a potted module. Packaging in small black boxes allowed for integration with a circuit

Brief History � 1963: First monolithic IC Op-Amp, the μA 702, designed by Bob Widlar at Fairchild Semiconductor. Monolithic ICs consist of a single chip � 1968: Release of the μA 741 The μA 741 became the canonical Op-Amp, from which many modern op-amps base their pinout from, and is still in production today. Parameter Range Frequency Spectrum 5 -k. Hz to beyond 1 -GHz GBW Supply Voltage 0. 9 V to a maximum 1000 V Input Offsets Approximately Zero

Presentation Outline � Introduction � Characteristics of Ideal and Real Op-Amps � Basic Circuits of Op-Amps � Applications � Exercise

Basic Op-Amp (Open-Loop) �

Ideal Op-Amp Parameter Name � Input impedance Output impedance Open-loop gain Bandwidth Symbol Value

Real Op-Amp Parameter Name � Input impedance Output impedance Open-loop gain Bandwidth Symbol Value

Saturation Vout � Vsat+ Slope = G Vin Vsat- Saturation Cutoff Points

Presentation Outline � Introduction � Characteristics of Ideal and Real Op-Amps � Basic Circuits of Op-Amps � Applications � Exercise

Open Loop vs. Closed Loop �A closed-loop op-amp has feedback from the output back to one of the inputs, whereas an open-loop op-amp does not. Open-Loop Closed-Loop

Negative vs. Positive Feedback � Negative feedback connects the output to the inverting input (-), whereas positive feedback connects the output to the non-inverting input (+). Negative Feedback Positive Feedback

Negative vs. Positive: Output � Negative feedback op-amps can produce any voltage in the supply power range. � Positive feedback op-amps can only produce the maximum and minimum voltages of the range. Vout Vsat+ Vin Vsat. Negative Feedback Vin Vsat. Positive Feedback

Inverting Op-Amp �

Non-Inverting Op-Amp �

Integrating Op-Amp �

Derivative Op-Amp �

Differential Op-Amp �

Summing Op-Amp �

Presentation Outline � Introduction � Characteristics of Ideal and Real Op-Amps � Basic Circuits of Op-Amps � Applications � Exercise

Applications �Active filters Signal processing Digital Image processing �Strain gauges �Control circuits PID controllers for aircraft PI controllers for temperature measurement circuitry �And much more…

Low-Pass Filter � High-Pass Filter

Bandpass Filter Notch Filter

Strain Gauge Strain gauges consist of a pattern of resistive foil mounted on a backing material. � As the foil is subjected to stress, the resistance of the foil changes in a defined way. � This results in an output signal directly related to the stress value, typically a few millivolts. � Op-Amps are utilized to amplify the output signal level to 5~10 V, a suitable level for application to data collection systems. �

PID Controller �

PID Controller �

And much more… �Comparators �Detectors Threshold detector Zero-level detector �Oscillators Wien bridge oscillator Relaxation oscillator �Level shifters

Presentation Outline � Introduction � Characteristics of Ideal and Real Op-Amps � Basic Circuits of Op-Amps � Applications � Exercise

Exercise �

References � � � � � Cetinkunt, Sabri. Mechatronics. Hoboken, NJ: John Wiley & Sons Inc. , 2007. Jung, Walter G. Op Amp Applications Handbook. Analog Devices, Inc. , 2005. “Operational Amplifier. ” http: //en. wikipedia. org/wiki/Operational_amplifier. “Operational Amplifier Applications. ” http: //en. wikipedia. org/wiki/Operational_amplifier_applications. “The Strain Gauge. ” http: //web. deu. edu. tr/mechatronics/TUR/strain_gauge. htm. “The PID Controller. ” http: //en. wikipedia. org/wiki/PID_controller. “Feedback in Electronic Circuits: An Introduction. ” http: //ecee. colorado. edu/~ecen 4827/lectures/dm_feedback 1. pdf. “Differentiator and Integrator Circuits” http: //www. allaboutcircuits. com/vol_3/chpt_8/11. html. “Inverting Op-Amp” http: //www. wiringdiagrams 21. com/2009/12/17/basicinverting-op-amp-circuit-diagram/

The End �Questions?