What will be the output voltage of an Op-amp inverting adder

Q.  What will be the output voltage of an Op-amp inverting adder for the input voltages V1 = -10V, V2 = +10V, V3 = +5V and resistances R1 = 600K Ω, R2 = 3000K Ω & R3 = 2M Ω  if the feedback resistance is considered to be 2M Ω?
- Published on 26 Oct 15

a. -38.3V
b. 38.3V
c. 40V
d. -40V

ANSWER: -38.3V
 
Given data:
V1 = -10V, R1 = 600k
V2 = 10V, R2 = 300K
V3 = 5V, R3 = Rf = 2M

The output voltage of an inverting adder or summer circuit is evaluated by,

Vo = -(K1V1 + K2V2 + K3V3)

where, 'K' represents the constant gain factor.
K1 = Rf / R1 = 2M/ 600K = 2000K/ 600K = 3.33
K2 = Rf / R2 = 2M/300K = 2000K/ 300K = 6.66
K3 = Rf / R3 = 2M/ 2M = 1

Therefore, Vo = -(K1V1 + K2V2 + K3V3)
= -[3.33 x (-10) + 6.66 x (10) + 1 x 5]
= -[-33.3 + 66.6+ 5]
= -38.3 V

Hence, the final output value of voltage of an inverting amplifier is nothing but summation of all input voltages estimated to be in terms of negative voltage of about -38.3 V.

Related Content

➨ Post your comment / Share knowledge


Enter the code shown above:

(Note: If you cannot read the numbers in the above image, reload the page to generate a new one.)
▲