Rectifier diode

Discussion in 'General Electronics Chat' started by DexterMccoy, Mar 25, 2014.

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  1. DexterMccoy

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    Feb 19, 2014
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    CR19 diode cuts off the negative cycle , leaving just a positive pulsing waveform?

    Does it cut off the whole negative cycle or just limits the amplitude of the negative cycles? creating a Half wave waveform

    Is CR19 a rectifier diode?

    Because I thought a rectifier diodes was in series not in parallel
     
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  2. DexterMccoy

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    Feb 19, 2014
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    CR18 only turns ON when the output of AR2 op amp LM101 output pin#6 is more or less Positive then R41 3K resistor tied to -10 volts?

    When CR18 turns ON , Rinput R17 10K is in a gain ratio with R40 ( 1.3K )

    R17 = Rin
    R38 = R feedback

    R17 = 10K
    R38 = 4.99K
     
  3. DexterMccoy

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    Feb 19, 2014
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    Here is the schematic
     
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  4. wmodavis

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    Oct 23, 2010
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    Schematics are much easier to read when right side up.
     
  5. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    He is entitled to answers from the forum. He doesn't have time to arrange his attachments correctly before posting them. We're supposed to download and flip them for him! Everything he attaches is side ways, part of the game.
     
  6. MrChips

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    Oct 2, 2009
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    You could also supply a sideways answer.
     
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  7. wmodavis

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    When posing a question and/or solution or a proposal, clear, precise communication rises to the top of the list as to what gets helpful answers, comments or even consideration.
     
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  8. Dodgydave

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    Jun 22, 2012
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    Can you invert your photo, or type your question upside down instead!
     
  9. DexterMccoy

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    Feb 19, 2014
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    Here is the schematics again

    What does CR18 diode do?

    What does CR19 diode do?
     
  10. DexterMccoy

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    Feb 19, 2014
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    What does CR57 & CR58 diodes do

    It clamps the negative cycles voltage, but for what reason?

    The pitch servo sums output goes to R148 resistor to U30 input

    Why use CR57 & CR58 to clip clamp the negative cycles voltage for what reason?
     
  11. DexterMccoy

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    Feb 19, 2014
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    I think they call these types of diodes that are on the output a SHUNT NEGATIVE CLIPPER

    But I don't know why they need to Shunt the negative cycle of the waveform on the Pitch Servo Sum output for the Pitch servo sums input
     
  12. Dodgydave

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    Jun 22, 2012
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    is the circuit faulty, or are you just curious as to how it works?
     
  13. DexterMccoy

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    Feb 19, 2014
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    Both, do you know how it works? please explain
     
  14. Dodgydave

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    What is it, what is not happening , also can we see the full diagram, what is the number of the op amp UA709?
     
  15. daviddeakin

    Active Member

    Aug 6, 2009
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    CR19 protects Q1 from large negatve base-emitter voltages, which might otherwise damage it. CR57 and CR58 might be doing the same thing; it depends what the RATE LIMIT and PITCH SERVO circuits are.
     
  16. DexterMccoy

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    Feb 19, 2014
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    Why would a negative cycle or negative voltage damage a transistor or op amp?/
     
  17. daviddeakin

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    Aug 6, 2009
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    Many transistors can only withstand -5V of reverse bias voltage before they are at risk of breakdown.
     
  18. DexterMccoy

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    Feb 19, 2014
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    Why can transistor take a higher positive voltage then a negative voltage? Can a high large negative voltage damage the input stage of an op amp?
     
  19. daviddeakin

    Active Member

    Aug 6, 2009
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    The base-emitter junction is a diode. Nothing more, nothing less. And like any diode, if you make the reverse voltage too large, it breaks down.
    It doesn't really 'withstand' positive (forward) bias voltages; that's just its normal operating mode.

    Yes absolutely. Sometime you find a pair of diodes connected in anti-parallel between the inputs of an opamp, to prevent the voltage between the inputs from being too great. Opamps like to have their inputs at the same voltage; they don't like to have them pulled apart like a comparator (although FET opamps will withstand such differential voltages more than BJT opamps).
     
  20. DexterMccoy

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    Feb 19, 2014
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    But when u have these clamping diodes only on the negative cycle voltage, it clips or shunts the negative cycle off which means the signal is a pulsing half wave form going to the input of a transistor or oop amp. Yes the diode protects it from a large negative voltage bbut it changes the waveform into a pulsing waveform
     
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