brief ppt on summing amplifier

1. Gandhinagar Institute of
Technology(012)
Subject : B.E. (2110016)
Active Learning Assignment
Branch : Computer
DIV. : A-3
Prepared by : - Vishvesh jasani (160120107042)
Guided By: Prof. Sajan Chourasia
Topic Name: Summing Amplifier

2. CONTENT
• Inverting Summing Amplifier
• Non inverting Summing Amplifier
• Equations
• i/o relationship

3. INVERTING SUMMING AMPLIFIER
“A summing amplifier is an op amp circuit that combines several
inputs and produces an output that is the weighted sum of the inputs”
An inverting Summing Amplifier is one whose output is the inverted
sum of the constituent inputs.
Besides amplification, the op amp can perform addition and
subtraction.

4. • The summing amplifier, shown in figure, is a variation of the
inverting amplifier.
• it takes advantage of the fact that the inverting configuration can
handle many inputs of the same time.

5. • Figure shos an OP-AMP used as
inverting summing amplifier signals.
• v1,v2,v3 are fed through resistor R1,R2
and R3 respectively to the inverting
terminal.
• the non inverting terminal is connected
to the ground.G is the virtual ground and
Rf is the feedback resistor.

6. • the current entering each op amp input is
zero. Applying KCL at node Agives
• 𝑖 =𝑖1 + 𝑖2 + 𝑖3
But
𝑖1=( 𝑣1 − 𝑣 𝑎)
1
𝑅1
, 𝑖2=( 𝑣2 − 𝑣 𝑎)
1
𝑅2
-----(a)
𝑖3=( 𝑣3 − 𝑣 𝑎)
1
𝑅3
,𝑖4=( 𝑣4 − 𝑣 𝑎)
1
𝑅4
----(b)
We note that 𝑣 𝑎=0 and substitute Eq. (a) into
Eq. (b). We get
𝑣0 = −(
𝑅 𝑓
𝑅1
𝑣1 +
𝑅 𝑓
𝑅2
𝑣2 +
𝑅 𝑓
𝑅3
𝑣3 )---(C )

7. If we consider that all the input resistor are having the
same resistance
i.e., R1=R2=R3=R
Then,
Hence the output is some constant factor times the sum of
the the inputs.

8. Further if we make Rf = R, then
-Vo = (V1+V2+V3)
Or Vo=-(V1+V2+V3)
This shows,the output voltage is equal to the sum of three input
voltage. It is important to note that the sign indicates that the output is
inverted with respect to the output
In a summing amplifier, the output is the weighted sum of the
Inputs.