Linear stabilizer

Discussion in 'Homework Help' started by Ron Potashnik, Mar 12, 2016.

  1. Ron Potashnik

    Thread Starter New Member

    Dec 27, 2015
    15
    0
    hello. i have questions about this linear stabilizer circuit.

    1)what is the need of a capacitor and why dose he so important in this circuit?
    2)why cant i charge the circuit more than 13v in a load test?
    3)why R1 have to be big resistor(4.7k)? what is the purpose of the resistor R5?
    tnx
    1.png
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,140
    1,790
    3) R1(4.7K) limits the current through the zener diode.

    You don't specify the input voltage range or the output voltage range so the other questions are hard to answer.

    IMHO, the 741 does not really like single supply operation and there should be a bypass cap on the supply pins.
     
  3. anhnha

    Active Member

    Apr 19, 2012
    773
    47
    The big output capacitor along with output resistance of LDO will be the dominant pole of the system. This makes it easier to compensate compared with one without output capacitor.
     
  4. Jony130

    AAC Fanatic!

    Feb 17, 2009
    3,957
    1,097
    But this circuit is not a LDO type.
     
  5. anhnha

    Active Member

    Apr 19, 2012
    773
    47
    From this page, it is an enhancement of transistor regulator. I think it can be called a type of LDO. The only different I notice is that in LDO the BJT transistor is not a voltage buffer as above. So maybe no compensation is necessary for this.
     
  6. Jony130

    AAC Fanatic!

    Feb 17, 2009
    3,957
    1,097
    This circuit with NPN transistor (series pass regulator) is "very far away" from low dropout regulator (with PNP ) and usually needs no output capacitor for stability.
     
  7. WBahn

    Moderator

    Mar 31, 2012
    17,743
    4,792
    Since this IS Homework Help -- how about hearing YOUR thoughts on what might be the answers to the rest of your questions?
     
Loading...