ultra sonic sensor module

i m trying to build an ultrasonic sensor(40khz) module using 8051/52 microntroller.
I need an ultrasonic receiving amplifier ckt so tat the out voltage of the amplifier s fed to the microcontroller with suitable voltage as input.The output from the receiving amp should be of 5v.I tried with ua741,lm2904,lm393 but,the output voltage of the amplifier drops to few mV at 40khz.Plz help me wit the suitable amplifier ckt so tat it gives me min of 3.5v which is given as input to microntroller.

If you are just trying to do some ultrasonic rangefinding and don't need to necessarily build you own, I would suggest the MaxSonar sensors from Maxbotics (Maxbotix Home- MaxBotix Inc., High Performance Ultrasonic Range Finders and Industrial Grade Ultrasonic Range Sensors). These sell for ~$25 US from places like Sparkfun, and they provide both an analog and serial output for distance.

The if your micro controller has either an A/D or a UART you could interface to one of these easily.