Voltage regulation

Discussion in 'General Electronics Chat' started by msrav1, Sep 27, 2008.

  1. msrav1

    Thread Starter Member

    May 26, 2008

    Do all ICs need voltage regulation? More to my concern, do high precision op amps, instrumentation amps, need regulated power supplies?

    At the moment I am using an INA118, a dual supply inst-Amp, I am using a 9V battery with a precision virtual ground IC TL246, to split the voltage to get +-4.5V.

    If I need regualted voltage, then I plan to use an LM317 to get a regulated 6 V and split it to 3V. (I believe getting more than 6V out of an LM317 with a 9V battery will not give reliable voltages over time)

    I'd prefer if I didnt need a regualted voltage, but not sure if I do?

  2. scubasteve_911

    Senior Member

    Dec 27, 2007
    The output of the opamp is a function of the input voltage, to a point where it is close to the supply rails. As long as your respect the basic specifications of the amplifier, it will work regardless if your supply voltage has gone down.

    I think your part number is incorrect, TL246, please confirm this. Is this a series or shunt reference?

    Adding a linear regulator can actually introduce noise, limited output range, and power loss into the circuit. So, don't do it unless you need to.

  3. mik3

    Senior Member

    Feb 4, 2008
    Don't use a regulator but because the battery's voltage will drop with time assume that the maximum output voltage of the op-amp is about 7.5V due to the fact that the battery voltage decreases with time and because the op-amp can not output the full supply voltage due to internal voltage drops. Thus restrict your output working voltage at about 7.5V and it will be fine.
  4. SgtWookie


    Jul 17, 2007
    Brand new commercial alkaline 9v batteries generally have an output of about 8.6v. Some industrial 9v batteries put out nearly 10v.

    With a 10k Ohm load, worst case scenario for an INA118 is V+ -1v, V- +0.35v. Typical is V+ -0.8v, V- +0.2v.

    Note that a 9v battery has a fairly high internal resistance, due to the construction (six small batteries connected in series) and have a relatively small mAh rating. Keep the load on it light for maximum battery life.
  5. hgmjr

    Retired Moderator

    Jan 28, 2005
    I agree with those that recommend avoiding the use of a linear voltage regulator. Their use will decrease the useable voltage output from the batteries.

    Did you consider using a couple of 9V batteries in an arrangement that would provide you with a built in reference? This would permit you to forego the need for the TL246?

    Maybe you could post a schematic of your circuit so that we could be more precise with our comments.

  6. Audioguru


    Dec 20, 2007
    An ordinary regulator needs an input 2V to 3V higher than its output. A low-dropout regulator needs an input only 0.5v higher than its output.

    A 9V alkaline battery voltage drops quickly to 7.2V where it is too low for an ordinary voltage regulator but can drop even lower if a low dropout regulator is used.

    Guess why I use a low dropout regulator with all my 9V powered circuits that need regulation?