ultrasonic sensor at 40 KHz

[himanshu0128]

• hi guys..just need a little help. i made a receiver circuit(shown in the image) for the ultrasonic sensor at 40 KHz. it works fine and my max. output is 3V. However I want to replace the transistor with opamp. Pls suggest some circuit.
• i have already tried using LM741 but it dint give desired results to due its limited bandwith gain..Kindly suggest a circuit using TL081 keeping in mind the 40KHz signal and desired gain of atleast 75.
• 
  
• The receiver module is connected between the capacitor(+pin) and ground(-pin).

 

[Colin Mitchell]

What gain are you getting.

Increase the 48k to 470k and 18k to 220k

 

[himanshu0128]

i m getting a gain of around 100 with this. But I want to replace it with an OPAMP only..

 

[Colin Mitchell]

Why?

 

[himanshu0128]

becoz my GUIDE insists for it..
also I will have to interface it with LED display and arduino later on..
Please help me..

 

[AnalogKid]

What is a GUIDE? Is this a homework problem?

That is a gain-bandwidth of 3 million. That's a lot. The TL081 datasheet says this is the max value for the part, so it would be operating open loop (not god). You will get better results with a compound amplifier, basically two amps in series. With a 10 V single supply and normal AC coupling techniques, two standard AC non-inverting opamp gain stages in series will work. TL081 datasheet, figure 27 (AC distribution amplifier), left half.

ak

 

[himanshu0128]

This is not a homework problem. this is my project..using amplifiers results in my received sine wave distorted to triangular wave..so its not working out.
nd gain bandwidth of 1 MHz is less for me because practically i cannot get more than 10 gain.
my receiver receives signal of amplitude less than 20 mV.

 

[Colin Mitchell]

"This is my project..using amplifiers results in my received sine wave distorted to triangular wave..so its not working out.

And gain bandwidth of 1 MHz is less for me because practically I cannot get more than 10 gain.
my receiver receives signal of amplitude less than 20 mV."

I don't know what you are talking about.

 

[GPG]

Show circuit of transmitter

 

[himanshu0128]

Show circuit of transmitter

Transmitter is working fine...It Produces square pulse of 10Vp-p with 65% duty cycle..16us on time and 8us off time..Receiver circuit is a problem here..pls suggest a circuit using opamps..nt transistor..my opertaing frequency is 40KHz..
thank you

 

[AnalogKid]

Crystals do not like DC bias. The transmitter waveform should be 50% duty cycle.

Again, datasheet, page 16, Figure 27, left half (AC distribution amplifier). See post #6.

http://www.ti.com/general/docs/lit/getliterature.tsp?genericPartNumber=tl081&fileType=pdf

ak