Noninverting Configuration - 14180_111
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CLOSED-LOOP OPERATION OF AN OPERATIONAL AMPLIFIER - 14180_110
Figure 3-16.Noninverting configuration
Neets Module 08-Introduction to Amplifiers
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Since no current flows into or out of the inverting input of the operational amplifier, any current
reaching point A from R1 must flow out of point A through R2. Therefore, the input current (I
_{in}
) and the
feedback current (I
_{fdbk}
) must be equal. Now we can develop a mathematical relationship between the input
and
output signals
and R1 and R2.
Mathematically:
If you multiply both sides of the equation by R1:
If you divide both sides of the equation by E
_{out}
:
By inverting both sides of the equation:
You should recall that the voltage gain of a stage is defined as the output voltage divided by the input
voltage:
Therefore, the voltage gain of the inverting configuration of the
operational amplifier
is expressed by
the equation:
(As stated earlier, the minus sign indicates that the output signal is 180 degrees out of phase with the
input signal.)
Noninverting Configuration
Figure 3-16 shows a
noninverting configuration
using an operational amplifier. The input signal (E
_{in}
)
is applied directly to the noninverting (+) input of the operational amplifier. Feedback is provided by
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