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Amplifiers power consumption ambiguity

In LT1994 by 150 diff load and 3.3 single supply yo can see this:

At the right side of picture you see "power". It says 23.1mA into Vcc! and 18.8mA from Vee!

First OpAmp must sink current from Vcc not sourcing to it!!!! secound why these (from and to Vcc and Vee) are different? Third I must consider only Vcc for determining regulator current rating?

Also I have simulated it in Ltspice and I had seen that it sink from Vcc and source to Vee. but I don't know why the max Icc=23.1mA is not equal to Iee=-21.4mA.

  • Hi Mohammad:

    First, I agree those seem to be backwards.  It would be correct if it referred to the pin currents, but the pins are Vs+ and Vs-, and from the schematic "Vcc" and "Vee" clearly refer to the supplies not the pins.  So I agree with you and am looking for the author of the calculator.

    Second, in a diff amp, when Vocm is not = to Vicm, then there are DC currents back through the input resistors and into the signal sources.  In this case, Vicm=0 and Vocm=1.65, so Idc back through the resistors is

    Idc = 2*1.65/(604+332) = 3.526mA

    Third, yes, you only need a positive regulator because you are only supplying Vcc, and Vee=ground.

  • Hi, thank you so much.
    In third Q, I don't need to take Vcc current into account for positive regulator budget. I need only Vcc, isn't that?