Low Frequency Amplifier

Discussion in 'The Projects Forum' started by thetallstewy, Oct 30, 2009.

  1. thetallstewy

    Thread Starter New Member

    Oct 30, 2009
    Alright, we are a senior design group building a low frequency ultrasound reciever system. We need to amplifiy the signal from the transducers.

    So we need a two channel low frequency amplifier .25MHz to 1.5MHz with 30dB gain.

    We used this site with these inputs(fc=1000000, B=500000, A=7.5, C=.470), but it doesnt we dont have enough gain for our range. Any ideas? Thanks in advance!
  2. studiot

    AAC Fanatic!

    Nov 9, 2007
    Need more data

    Impedance level of signals?
    voltage level of signals (are they voltage or current; some ultrasonic transducers are current driven)?
    is signal earth referenced?
    Load impedance to be driven?

    What op amp did you try in your simulation?
  3. thetallstewy

    Thread Starter New Member

    Oct 30, 2009
    Used a 741 opamp. Our peak to peak is .4V.

    The transducers are powered through circuitry. We are using Olympus immersion trandsducers V303 and V301.
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    Can you be serious? -
    And you say -
    - to cover the range
    - with -
    This is less than believable. Look at the specs on a 741.
  5. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
    Whenever I see "We" it's either a school project or the Borg. The Borg stopped using the 741

    AAC Fanatic!

    May 26, 2009
    I'll second that, are you serious!?

    Any ultrasound receiver is going to require a high-speed op-amp. I'd find the right op-amp first that can concur with your application before anything else.

  7. studiot

    AAC Fanatic!

    Nov 9, 2007
  8. thetallstewy

    Thread Starter New Member

    Oct 30, 2009
    Please be constructive all. For the past 5 years, in every lab with op amps, I have used the 741, and actually my labs suck at teaching the "guts" of an op amp, so I figured it would be a start.

    So studiot, I will check out those series, thank you.
  9. thetallstewy

    Thread Starter New Member

    Oct 30, 2009
    Alright, so I looked through the op amps I have access to and best I can find is the TL0xxCP series. Are these fast enough or do I have to order the LT1630? Thank you
  10. ziouranio


    Jul 23, 2009
    Hi, I usually work with ultrasound for diagnostics and when performances are the issue nothing can beat specific purpouse IC devices.
    They are costly but if your application is not a consumer device but a high-end product such as for medical diagnostics or test equipment, the time you will save in design phase and the increase in performances will pay many times the cost increase.
    Some yars ago I used the AD600 (Analog devices) that is a 2 stage amplifier up to 40+40dB with 35MHz bandwidth. The interesting thing is that you can change the gain from 0 to 80dB with a plain voltage control (like the DAC output of your MCU).
    I also used AD603 (90MHz) and the logarithmic AD606 with great results. The only problem is prince, ranging from 20-30$ for AD603 to more than 100$ for AD606.
    I am going to use the 40MHz VCA2614 (Texas Inst.) for my next designs or its 80MHz VCA2616 brother.
    Choosing one of these IC you will only need an impedance buffer front-end for the piezoelectric transducer, any JFET input op-amp with low noise and suitable speed will be a proper choice for this.
    Hope this helps.
  11. SgtWookie


    Jul 17, 2007
    The TL0xx series are basically for the audio range. A TL07x gain bandwidth product is 3MHz (that's with unity gain, or gain=1) - you need 10x that bandwidth.

    The LT1630 should work for you.