Question

An input of Vsinωt is applied to an ideal frequency doubler. Compute its output voltage?

(a) Vo = [(Vx×Vy) /Vref^2] × [1-cos2ωt/2].

(b) Vo = [(Vx^2×Vy^2) /Vref] × [1-cos2ωt/2].

(c) Vo = [(Vx×Vy)^2 /Vref] × [1-cos2ωt/2].

(d) Vo = [(Vx×Vy) /( Vref] × [1-cos2ωt/2].

This question was posed to me during a job interview.

My query is from Multiplier and Divider topic in portion Operational Amplifier Applications of Linear Integrated Circuits

Answer 1

Right answer is (d) Vo = [(Vx×Vy) /( Vref] × [1-cos2ωt/2].

Discover the easiest explanation: In an ideal frequency doubler, same frequency is applied to both inputs.

∴ Vx = Vxsinωt and  Vy = Vysinωt

=> Vo = (Vx×Vy × sin^2ωt) / Vref = [(Vx×Vy) / Vref] × [1-cos2ωt/2].