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Slew RateIn Mechanics the slew rate is given in dimensions and is associated with the change in position of an object over time which is orbiting around the observer. In Electronics, the slew rate is a nonlinear effect in operational amplifiers. It represents the inability of the amplifier output to keep up with rapid changes in input. Definition The slew-rate of an op-amp is defined as the maximum rate of change of the output voltage for all possible input signals. -
Slew rate is typically expressed in units of V/μs. Origin of slewing There are slight differences between different op-amp designs in how the slewing phenomenon occurs. However, the general principles are the same as in this illustration. The input stage of an op-amp is a differential amplifier with a transconductance characteristic. This means the input stage takes a differential input voltage and produces an output current into the second stage. The transconductance is typically very high - this is where the large gain of the op-amp arises. This also means that a fairly small input voltage can cause the input stage to saturate. In saturation, the stage produces a nearly constant output current. The second stage of an op amp is, among other things, where frequency compensation is accomplished. The low pass characteristic of this stage approximates an integrator. A constant current input will therefore produce a linearly increasing output. If the second stage has an input capacitance C and gain , then slew rate in this example can be expressed as: -
where is the output current of the first stage in saturation.
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