An inverting scaling amplifier has three input voltages Va, Vb and Vc. Find it output voltage?
(a) VO= – {[(RF/Ra)×Va] +[(RF/Rb)×Vb]+[(RF/Rc)×Vc]}
(b) VO= – [(RF/Ra)+(RF/Rb)+(RF/Rc)]×[( Va +Vb+Vc)].
(c) VO = – {[(Ra/RF)×Va] +[(Rb/RF)×Vb]+[(Rc/RF)×Vc]}
(d) None of the mentioned
I had been asked this question in an online interview.
My doubt stems from Summing, Scaling & Averaging Amplifier in portion Operational Amplifier Applications of Linear Integrated Circuits