Operational Amplifier
Operational Amplifier
An Operational Amplifier or op-amp is a high gain differential amplifier with high input impedance and low output impedence.
are to provide voltage amplitude changes (amplitude and polarity), oscillators,
filter circuits, and many types of instrumentation circuits. An op-amp contains a number
of differential amplifier stages to achieve a very high voltage gain
Figure shows a basic op-amp with two inputs and one output each input results in either the same or an opposite polarity (or phase) output, depending on whether the signal is applied to the plus (+) or the minus (-) input.
Single-Ended Input
Single-ended input operation results when the input signal is connected to one input
with the other input connected to ground.
When the input is applied to the non-inverting terminal or plus(+) terminal with the inverting or minus(-) terminal at ground, the output will have the same polarity as that of the input signal, If the input is applied to the inverting or minus(-) terminal and the non-inverting or plus(+) terminal is grounded the output will be in opposite phase to the input signal
Double-Ended (Differential) Input
When an input is applied to both the terminals of an op-amp it is called a Double-Ended (Differential) Input.
A voltage Vd is applied between the two terminals, Vd is called the differential voltage and is equal to the difference of the input voltages at the two input terminals. So, mathematically,
The resulting amplified output in phase with that applied between the plus and minus inputs.
(Note: None of the inputs are grounded in this case)
Double-Ended Output
The op-amp can also be operated with opposite outputs, An input applied to either input
will result in outputs from both output terminals, these outputs always being opposite
in polarity
Differential Amplifier Circuits Using Transistors
Common Mode Rejection Ratio(CMRR)
DC Bias
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