# Help!! - Design an amplifier circuit

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#### truthteller

##### Newbie level 1
I am a first year student in electrical engineering.
i'm having a difficulty starting my project which is to design and build a Summing Amplifier
that i am assuming... i would appreciate any help ...

Design an amplifier circuit so that vo = v a + v b + v c .
Show the schematic and all calculations.

Last edited:

#### Junus2012

hello
use the inverting summing op-amp attached

set Rf to 100 KOhm
Ra=12.5 KOhm ......(8va)
Rb= 50 KOhm .......(2Va)
Rc = 25 KOhm .......(4Vc)

the output voltage expression is Vo=-(Rf/R1.va+Rf/R2.vb+Rf/R3.vc)

if you would like to remove the negative sign from the output then use an inverting amplifier at the output of this amplifier with unity gain

Points: 2