LM741 with LM2907

Discussion in 'The Projects Forum' started by onlyvinod56, Feb 20, 2012.

  1. onlyvinod56

    Thread Starter AAC Fanatic!

    Oct 14, 2008
    Iam designing speedometer using LM2907(16 pin).
    I have used IR led pair as speed sensor. When the motor speed is changed from minimum to maximum, the 2907 (f~V converter) gave an output voltage of 0v to 1.2v.

    I want a little bit more voltage. From the datasheet of 2907....the Vo can be expressed as
    Vo = Vcc x R x C. I have changed the R and C values but im not satisfied with the results.

    Can i connect a 741 opamp to have a voltage gain? Do the opamp amlifies the DC voltage? Iam readily having the 741 now. And my circuit os not having a dual supply.
  2. MrChips


    Oct 2, 2009
    If you have been following some of the other posts, the LM741 is a 44-year old design that is ubiquitous in all the electronics textbooks. Drop the 741 and move up to a newer op amp that operates on a single supply. I am not a expert in this regard but the LM358 is a popular dual op amp. Others may suggest some other op amps.

    Yes the op amp will amplify the DC component also. You have to remove the DC component before amplifying.
  3. Wendy


    Mar 24, 2008
    The LM358 has one advantage over a 741, it will almost go to ground on the inputs and still respond properly. Minor, but great for many projects. The power supply is also better defined.

    In most ways, it is a souped up 741, only slightly better in most regards.

    A speedometer? Remember the terms of our TOS, no automotive.