Introduction Characteristics of Ideal and Real Op-Amps Basic
Circuits of Op-Amps Applications Exercise
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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.
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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 dB 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 15V to 10V 1962: Op-Amp in a
potted module. Packaging in small black boxes allowed for
integration with a circuit
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1963: First monolithic IC Op-Amp, the A702, designed by Bob
Widlar at Fairchild Semiconductor. Monolithic ICs consist of a
single chip 1968: Release of the A741 The A741 became the canonical
Op-Amp, from which many modern op-amps base their pinout from, and
is still in production today. ParameterRange Frequency
Spectrum5-kHz to beyond 1-GHz GBW Supply Voltage0.9 V to a maximum
1000 V Input OffsetsApproximately Zero
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Introduction Characteristics of Ideal and Real Op-Amps Basic
Circuits of Op-Amps Applications Exercise
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Parameter NameSymbolValue Input impedance Output impedance
Open-loop gain Bandwidth
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Parameter NameSymbolValue Input impedance Output impedance
Open-loop gain Bandwidth
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V in V out V sat+ V sat- Saturation Cutoff Points Slope =
G
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Introduction Characteristics of Ideal and Real Op-Amps Basic
Circuits of Op-Amps Applications Exercise
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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-LoopClosed-Loop
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Negative feedback connects the output to the inverting input
(-), whereas positive feedback connects the output to the
non-inverting input (+). Positive Feedback Negative Feedback
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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. V in V out V sat+ V sat-
Negative Feedback V in V out V sat+ V sat- Positive Feedback
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Introduction Characteristics of Ideal and Real Op-Amps Basic
Circuits of Op-Amps Applications Exercise
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Active filters Signal processing Digital Image processing
Strain gauges Control circuits PID controllers for aircraft PI
controllers for temperature measurement circuitry And much
more
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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.
