I want to design a circuit that turns on an LED when the frequency of the input signal is between 950-1050 Hz using only passive elements and op amps aside from the actual LED.
I have designed the band pass filter but I am stuck on the best way to make the LED turn on only when the input signal has the desired frequency since an input of 925Hz wont be attenuated significantly more than 950Hz. I should note that I want the input signal to have a DC offset of 2V and an amplitude range between 2 and 5 V for the sinusoidal portion.
My initial idea was to use an op amp with no feedback to turn the LED on however I also want the input signal to power the LED so it can then be detected by a photo transistor.
Is there a better way to do this?