If all four input resistors to a summing amplifier are 2.2 $\mathrm { k } \Omega$ and the feedback resistor is 2.2 $\mathrm { k } \Omega$. then the gain equals________
A) 4
B) 2.2
C) 1
D) unknown

Question

If all four input resistors to a summing amplifier are  2.2  $\mathrm { k } \Omega$ and the feedback resistor is  2.2  $\mathrm { k } \Omega$. then the gain equals________
A) 4
B)  2.2 
C) 1
D) unknown

Quizplus · Accepted Answer

In a summing amplifier, the gain is determined by the feedback resistor divided by the sum of the input resistors. In this case, the feedback resistor is also 2.2 kΩ, so the gain is:

2.2 kΩ / (2.2 kΩ + 2.2 kΩ + 2.2 kΩ + 2.2 kΩ) = 2.2 kΩ / 8.8 kΩ = 0.25

Since this is a non-inverting summing amplifier, the output will be the sum of the inputs multiplied by the gain, so:

Output = (Input 1 + Input 2 + Input 3 + Input 4) x 0.25

Therefore, the gain in this circuit is 0.25 or 1/4. Choice C is the only option that matches this result.

If All Four Input Resistors to a Summing Amplifier Are kΩ\mathrm { k } \OmegakΩ

If All Four Input Resistors to a Summing Amplifier Are $\mathrm { k } \Omega$