Frequency detection circuit

I have a signal with 5MHz frequency sine wave as input. I have to make a beep sound, whenever the frequency reduces to below 4.8 MHz. How can i do this using simple circuits? Anyone please help me. Is that possible using op-amp.

Also can u send a 5MHz crystal oscillator circuit diagram using opamp with the design.

minu.grg said:

Also can u send a 5MHz crystal oscillator circuit diagram using opamp with the design.

Click to expand...

a regular voltage feedback opamp will not work at 5Mhz, you need to use a current feedback (CFB) op amp... it's simpler to use a CMOS hex inverter as the oscillator. the output of an oscillator using a 4049 is going to be a square wave, but a low pass filter can be used to shape it into a sine wave. the output of the oscillator is monitored by a phase locked loop, and the control voltage for the VCO will be proportional to the input frequency. feed the control voltage into a comparator, and when it passes the threshold equivalent to the PLL operating at 4.8Mhz, the comparator triggers the alarm.