slew rate in opamp

Subject Code :151003
Name Of Subject Integrated Circuit and Application
Name of Unit :The Practical Op-Amp
Topic :Slew Rate & its equation
Name of Faculty : Mr. Jwolin Patel
Mr.Yogesh Parmar
Name of Students : (i) Savalia Avani(100870111020)
(ii) Patel Jay (100870111021)
Sub: ICA Topic: Slew Rate & its equation

Slew Rate and its equation


The Operational Amplifier
• Usually Called Op Amps
• An amplifier is a device that accepts a varying input
signal and produces a similar output signal with a
larger amplitude.
• Usually connected so part of the output is fed back
to the input. (Feedback Loop)
• Most Op Amps behave like voltage amplifiers. They
take an input voltage and output a scaled version.


• They are the basic components used to build analog circuits.
• The name “operational amplifier” comes from the fact that
they were originally used to perform mathematical
operations such as integration and differentiation.
• Integrated circuit fabrication techniques have made high-
performance operational amplifiers very inexpensive in
comparison to older discrete devices.


The Operational Amplifier
+VS

i(-) _
Inverting

RO
vid Output
Ri A
vO = Advid
Noninverting
i(+) +

-VS


• i(+), i(-) : Currents into the amplifier on the inverting and noninverting lines
respectively
• vid : The input voltage from inverting to non-inverting inputs

• +VS , -VS : DC source voltages, usually +15V and –15V

• Ri : The input resistance, ideally infinity
• A : The gain of the amplifier. Ideally very high, in the 1x10 10 range.

• RO: The output resistance, ideally zero

• vO: The output voltage; vO = AOLvid where AOL is the open-loop voltage gain


• In electronics, slew rate is a vector representing the
maximum rate of change of a signal.
• The slew rate of an electronic circuit is defined as
the maximum rate of change of the output voltage.
Slew rate is usually expressed in units of V/µs.

where is the output produced by
the amplifier as a function of time t.

•The slew rate can be measured using a
function generator (usually square wave) and oscilloscope.
•The unit of slew rate is typically V/µs.
•The slew rate is same for both when feedback Is
considered or not considered.


There are slight differences between different
amplifier designs in how the slewing
phenomenon occurs. However, the general
principles are the same as in this illustration.
The input stage of modern amplifiers is usually
a differential amplifier with
a transconductance characteristic.

This means the input stage takes a differential input
voltage and produces an outputcurrent into the second
stage.
The transconductance is typically very high — this is
where the large open loop gain of the amplifier is
generated. 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 modern power amplifiers is,
amongst 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 a compensation capacitance and gain , then
slew rate in this example can be expressed as:


Slew rate helps us to identify what is the maximum
input frequency and amplitude applicable to the
amplifier such that the output is not distorted. Thus it
becomes imperative to check the datasheet for the
device's slew rate before using it for high-frequency
applications.


slew rate in opamp

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