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bg8dmy

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Posts posted by bg8dmy



  1. in the latest version, the output of U3 drives D9 to reduce the output voltage to zero when the output is shorted. D9 has a forward voltage drop of about 0.7V so the output of U3 must be able to go a little below -0.7V. I used two diodes to make the negative supply for U3 at about -1.3V.

    A 3V zener diode or even a 5.6V zener diode can be used instead of the two diodes.

    Thanks~
    I did a  circuit, but found ineffective regulator, for example, in the 3A maximum current range, adjust the voltage of 20V, but the addition immediately after the load into 16V. What is the reason?


  2. You are trying to make the original circuit that does not work properly and has many overloaded parts.
    We fixed it and changed it and the new schematic and new parts list have been posted here many times.

    Your 25VAC transformer produces a positive unregulated voltage of only 34VDC which is too low. Your supply will produce a maximum regulated output of pnly 26VDC at 3A, not 30VDC.
    The new parts list has a 28VAC or 30VAC transformer and new 44V opamps. The new opamps work with no negative supply and a low voltage negative supply.

    Your idea has a positive 34VDC supply and a negative 5.6V supply which is a total of 39.6VDC when there is a full 3A load and a total of maybe 43VDC when there is no load.
    But the original TL081 opamps and the ones you are talking about have an absolute maximum allowed total supply of only 36VDC.

    The new circuit has a positive supply that is +37.6V to +42.4V. It has a negative -1.3V supply for one opamp. Then its maximum total is less than the 44V max of the new TLE2141 or MC34071 opamps.
    The old opamp and the opamps you are talking about do not work without a negative supply or a negative supply as low as -1.3V.





    Thank you for your reply~
    Regards ~
    bg8dmy


  3. I do not know what you are asking.
    Many transformers have 4 windings so they can be used with 115VAC or 230VAC and can be 15V at high current or 30V at lower current.


    I did not express clearly
    I have a two-winding transformer secondary, double winding with center tap voltage 2X25V, I can use full-wave rectifier rectifier? Means that this part of the rectification circuit using only two rectifier diodes, rather than the full-bridge rectifier
    In addition, the circuit is able to use CA3140 LM741  operational amplifier?

    post-60295-14279144281681_thumb.png

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