Op amp circuit not amplifying properly, help

I have an issue.

I want to amplify a signal through 2 op amps. The feedback resistor is between the

pin and the output. (pin 2 and 6 of the 741op amp). The resistor ration (r2/r1) is 150. However, I only get an amplification of 5x. Different resistors for r2 yields the same result. I even changed the op amp, same issue.

The second op amp in the series works fine, but stage one refuses to function. The cap I am using is at 0.47uf and the feedback resistor is 1.5M.

What is the problem?

Above: This is what the circuit is based on.

Latch

0 jvdberg@ieee.org over 13 years ago

The internal resistance of the transducer must be added to the 10k resistor at the input of the first opamp. If the internal resistance of the transducer is 200 k-ohm, the gain is 5 * A solution for the low gain could be connecting the transducer to the non inverting input of the opamp.
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0 Latch over 13 years ago in reply to jvdberg@ieee.org

I did not think of that, thank you. I will see if that helps...

Latch
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0 RWM over 13 years ago in reply to Latch

You can find information about designing ampifiers for piezoelectric ultrasonic transducers there:
http://130.89.85.15/electronics/ultrasound/Low%20output%20noise%20amp%20for%20piezo%20trancdurs.pdf
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