An Op-Amp to amplify 1mV 40KHz signal upto almost 3.3V-5V

[alfie.max15]

In my project i have an ultrasonic receiver which gives an output of 1mV-10mV 40KHz signal
i need to trigger a pin of the microprocessor high when i receive this signal so...

I need an amplifier stage in between...
i tried an op-amp LM324 even though i get required uotmut in simulation, in real time i am not able to amplify any signal with Amplitude <100mV
For 100mV i am getting an amplification of 1000, i.e 1V

I need some other good fast responsive operational amplifier of instrumentation amplifier.

Please can anyone suggest some cheap and good IC's for this purpose,... Also i need to power it from my PC, so it should work in 5V

 

[BradtheRad]

It's possible your zero offset has to be raised a bit, so that it will then detect a weak incoming signal.

Although a single op amp has terminals built-in so we can adjust the zero offset, the quad 324 does not. So we must try a workaround. It ought to help if you were to apply a slight positive bias at the non-inverting input.

That is what I had to do when I used a 324 op amp to detect a very low voltage across a length of wire carrying current from my solar panels.

Screenshot:

 

[Nick_F]

You didn't specify if you use single power supply or dual power supply. For single supply, you need to apply V/2 to reference pin and the 1mV signal has to go through a capacitor to the other input. What is the circuit diagram? If you amplify a 100mV signal to 1V you only have a gain of 10x, not 1000x. I expect your LM324 should be able to amplify 1000x. Do you use only one opamp in the diagram or two in series? It's better if you use two opamps in series (each with a gain set to 32x).

Regards,
Nicolae