I'm designing an ultrasonic receiver circuit that should deal with a 10 mv signal( may be less !! the limitation here is due to the transducer itself http://www.ram-e-shop.com/ds/general/Ultra_Soinc.pdf ).
The signal is 40 Khz sinusoidal pulse-modulated signal (pulse duration=1.8 s; pulse width=83 ms) , and I used LM358 for multistage amplification, but I ended up after 4 stages of inverting amplifier configuration (each stage's gain is supposed to be 100; meaning R2/R1=100) with a 1 volt p-p signal and a 0.75v p-p noise !!
I need to get a 0-5 volt signal when I receive the 83 ms pulse, but I'm starting to think its not possible using commercial amplifiers.
Any suggestions on the opamp selection itself??
I also tried to use multistage BJT amplifier (CE configuration) and the signal to noise ratio was much better than the opamps, but the gain was not sufficient!
I tried to use a band pass filter at 40 khz to eliminate the noise, but no active filter using lm358 could be precise and a passive RC or RLC filter would kill the mv signal I want.
I used Multisim simulator before I implemented the circuit and it showed some satisfying results. However, when I use the discrete components (whose reliability is not guaranteed) and measure the results on an oscilloscope, its rather depressing results.
Any help with the amplifier or filter circuit would be much appreciated.
The signal is 40 Khz sinusoidal pulse-modulated signal (pulse duration=1.8 s; pulse width=83 ms) , and I used LM358 for multistage amplification, but I ended up after 4 stages of inverting amplifier configuration (each stage's gain is supposed to be 100; meaning R2/R1=100) with a 1 volt p-p signal and a 0.75v p-p noise !!
I need to get a 0-5 volt signal when I receive the 83 ms pulse, but I'm starting to think its not possible using commercial amplifiers.
Any suggestions on the opamp selection itself??
I also tried to use multistage BJT amplifier (CE configuration) and the signal to noise ratio was much better than the opamps, but the gain was not sufficient!
I tried to use a band pass filter at 40 khz to eliminate the noise, but no active filter using lm358 could be precise and a passive RC or RLC filter would kill the mv signal I want.
I used Multisim simulator before I implemented the circuit and it showed some satisfying results. However, when I use the discrete components (whose reliability is not guaranteed) and measure the results on an oscilloscope, its rather depressing results.
Any help with the amplifier or filter circuit would be much appreciated.