For curiosity reasons, I want to know why engineers used the term "slew rate" for this op-amp phenomenon, I mean "slew".
I googled it and found this: "turn or slide violently or uncontrollably".
What is the explanation?
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If "slew" is sliding violently or uncontrollably¹, the "slew rate" is the speed at which something slides violently or uncontrollably.
In an op amp, the slew rate is the maximum speed at which the output voltage can change; if you instantaneously change the input, the output voltage will "slide violently or uncontrollably" to the new stable point, and the speed at which that happens is called the slew rate. Due to how standard op amps work, the slew rate is approximately constant regardless of input or feedback characteristics, so it's a useful characteristic to put on the datasheet.
¹Since a number of people have said this is wrong, I feel I should note that this is not how I would define the word "slew". But the exact definition doesn't matter--the same argument holds whatever definition you use.
I think the term slew rate is derived from servo engineering which in turn acquired this from a nautical term which means to swing a gun or rigging about a vertical axis.
The Oxford English Dictionary uses as a reference for slew: 1962 L. A. Stockdale Servomechanisms vii. 112 The slewing time may form part of the servo specification, i.e. the servo to slew through 90° in the minimum time.
Slew derives from a nautical term, and you can find many 1800s references to slewing a cannon on its trunnions (that would be a vertical movement).
The earliest recorded usage (according to the OED) is from Falconer's Marine dictionary (1769):
To SLUE, is to turn any cylindrical or conical piece of timber about its axis, without removing it. This term is generally expressed of the movement by which a mast or boom is turned about, in its cap or boom-iron.
In the context of an amplifier, the slew rate is what you see when the input is overdriven and the output is changing as fast as possible. It's generally a linear slope (constant dv/dt) for an op-amp. If you have (say) a sine wave that is being distorted by slew rate limitation you may be able to reduce the distortion greatly by reducing the signal level (thus calling for proportionally less dv/dt). Bandwidth limitations will (ideally, anyway) equally affect large and small signals.
"Slew Rate" is the max. output slope e.g. ΔV/Δt = Io(max)/C(load) due to the internal current limiter.
This is regardless of the feedback at the maximum bandwidth of unity gain. In this sense, this becomes an open-loop like a comparator as it is "the uncontrollable maximum slope" except for the standard test load capacitance such as 20 pF and the internal regulated current limiter used for short circuit protection.
Generally in electronics slew rate is controlled by Io max and C load is not chaotic.
In some cases, low input and/or load resistance is needed to speed up to the specified max. rate as defined in the datasheet. Pay attention to the plots in the datasheet.
ΔV/Δt = Ic(max)/C load=20pF for a specified step input voltage and supply voltage at 25'C
Not all Op Amps have slew rate specs, although they may show a large signal response to a square wave. e.g. LM358 specs. show a large signal square response with a linear ramp of 2.5V/4us.
Op Amp slew rates can range from 400 µV/µs to 18200 V/µs.
For ESL users