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The GJ general purpose Gyrator / Regulator

Discussion in 'd.i.y.' started by geoffgjones, Sep 23, 2008.

  1. geoffgjones

    geoffgjones Member

    This is a simple version of the gyrator circuit that many people are using for thier cd players and pre-amps. It does not require a pre-regulator, as the zener maintains a stable voltage at the output. Further, it can be used for power applications as well, with almost any input / output voltage that is required, as long as the pass transistor can take it! The output voltage should not be any lower than 2v below the voltage of the zener. Additional filtering can be used before the drain of the Jfet, but I have not found this necessary, as the Jfet tends to deliver a clean voltage to C1. A highly effective circuit for both low and high power applications.

    The transistor types should be selected to taste...... Don't forget to increase the capacitor voltages as required.

    http://www.box.net/shared/bzkuk839mj

    Cheers,

    Geoff Jones
     
  2. geoffgjones

    geoffgjones Member

    72 views and no comments? Please try this simple circuit, I have it running the voltage gain stage (43 volts) on my PM17KI (a model I was involved with professionally). I have also tried it in my CD63KI for powering the opamps with great effect, better than anything else yet!

    Cheers,

    Geoff
     
  3. flashgo

    flashgo DIY Practitioner

    Thanks, Geoff. Need to order some bits. What's your spec for Q2? It's clipped off on your circuit diagram. I know it depends on the app, but I need a starting point. Cheers.
     
  4. randytsuch

    randytsuch Active Member

    Hi Geoff
    Would be nice if you could post a pic of a completed one, to help get an idea of how to put it together.

    Have you compared it to a teddyreg?

    I am using some teddy regs to power a discrete op amp stage, in my modded squeezebox, and am very happy with the sound I am getting.

    Randy
     
  5. geoffgjones

    geoffgjones Member

    Hi Flashgo,

    The ubiquitous D44H11 will do nicely, although I have had good results with the MJE520. Any low noise devices will be OK for the other transistors, including BC547C and J112 for the Jfet. Experimentation is easy with this circuit! I think that the loss of the LM317T gives the circuit a simplicity that you just can't complain about!




     
  6. geoffgjones

    geoffgjones Member

    Hi Randy,

    The regs I am using are withing my PM17KI, and buried somewhat. I am going to make a few more PCBs to power my CD5x over the weekend, so I will take some pics then. The sound is rather similar to the teddyreg, but with a slightly clearer top end, but slightly leaner lower end, perhaps because I am using a poor quality cap for C1. I think the top end cleanup is due to the loss of the 317, it does create some hi frequency noise, as it is an active opamp based regulator. I would think that exchanging the teddyregs with this one will make much difference at all. However, for power and high voltage apps, this circuit will win out, as you are not restricted with the max voltage of the 317 pre-reg. Plus for lower power regulation, there are far fewer components!

    Hang on! would you prefer a pic of one built onto a normal stripeboard? you could copy it far easier perhaps?

    Cheers,

    Geoff

     
  7. randytsuch

    randytsuch Active Member

    Hi Geoff
    Thanks for the quick response. A pic of one built on a stripboard would be good, to copy from.

    I am using a Teddy Powerreg to power my squeezebox, wonder how it would sound with you reg? Like I said before, things sound pretty good right now.

    How well does you GJ regulate over load? That was the one thing I don't like about the Teddy, I did not want to use a pot, so I had to tweak the 317 resistors, to get the voltage I wanted, with the actual load.

    How fast does you reg come up? For my squeezebox, I had to add the accelerator circuit, otherwise the voltage came up too slowly, and my SB would not turn on.

    Give me time, I'll think of some more questions ;)

    BTW, a catchy name would help :)

    Randy
     
  8. geoffgjones

    geoffgjones Member

    Hi Randy,

    The output voltage under load should be very stiff, expect +/- 0.5 variation only. the charge time is also very short, as the JFET works as a constant current supply, and charges the cap very fast as long as your input voltage is a handfull of volts over the required output voltage. I do not own an SB3, so please do the experiment and report back! BTW, make sure you heatsink the power transistor. The power requirement can be calculated as:

    (Vin - Vout) * Ic (the current required). Most power transisters will go up to 1Watt without heatsink, but even so will get very hot. Let me know what your Vin, Vout and Ic are, along with your power transistor type, and I will let you know what type of heatsink you require.

    Cheers,

    Geoff
     
  9. Baki

    Baki Active Member

    Probably a silly question but... could it be possible to change a Darlington for Fetlington in this reg?

    TeddyReg with Fetlington was a big improvement...

    Baki
     
  10. randytsuch

    randytsuch Active Member

    Hi Geoff
    My current powerreg I am using as a SB power supply has a pretty big heatsink, it gets about 10F over ambient, at most, so I think I am set for the heatsink.

    I need to collect the parts, but had a couple other questions.

    What would a negative voltage version look like?

    How much higher is the output voltage over the zener voltage?

    Randy
     
  11. geoffgjones

    geoffgjones Member

    Hi Randy,

    Will post a negative version ASAP.

    The voltage should be between 1.4 and 2 volts lower than the zener voltage.

    Will get back to you soon, busy weekend so far!

    Cheers,

    Geoff
     
  12. geoffgjones

    geoffgjones Member

  13. geoffgjones

    geoffgjones Member

    Have now tried this against a teddy Reg MKII and can confirm that the loss of the lm317 makes this circuit shine! A good (but not special) cap for C1 makes a difference. It can also be reduced to 47uF without loss of smoothing. I am extreeeeeemely happy with this circuit, and hope to know what others out there think!

    Cheers,

    Geoff
     
  14. ron

    ron Tweaker

    Interesting, thanks for sharing Geoff

    I'll give this a try later today if I have the parts, one thing I don't have for sure is the types of J-fet posted, I may have J309 and J310, maybe a BF245B and a 2sk107BL

    Whats the current you got through the CRD?
     
  15. Ciu

    Ciu New Member

    Hello !

    What is the output voltage, considered to the Zener voltage ?
    Thanks
    R.C.
     
  16. ron

    ron Tweaker

    I've quickly knocked it up on vero, using a 20v zener output is 19.5v.
    Transistors are Tip41C,BC184C , fet is a J309

    I haven't had chance to try it anything yet:) just fitted a 1k loading resistor

    [​IMG]
     
  17. bivalve

    bivalve pfm Member

    Geoff,

    Won't the Q2 Vbe and hence the output voltage vary with current fluctuations in regulators of this type?

    I accept that it sounds good so you are presumably juggling various parameters for a net good effect.

    David
     
  18. geoffgjones

    geoffgjones Member

    Sorry for not being around.

    1. a negative version will be posted ASAP.

    2. David: Q2 Vbe has some but very little effect, the voltage output being a little under the zener's voltage. The output current should, however, always be above a few (5 or 6) mA to ensure regulation (the Hfe of Q1 will also have a very small effect on this value).

    3. To get as low a noise value as possible get at least 2V overhead on the output.

    Dynamic regulation is as good as the zener, in other words excellent!

    More to come, must dash. Will post some images when I can,

    Cheers,

    Geoff
     
  19. neiljadman

    neiljadman Senior Member

    Are there any reports yet, I was thinking of giving it a go.
     
  20. 13mh13

    13mh13 pfm Member

    How much is "a little under the zener's voltage"?
    E.g. If one wants 5V out -- say, for powering ICs -- what zener voltage should one select? In Geoff's ckt, what is the sum of losses (voltage "dropouts") to consider?

    With respect to shunting, how about using a "precision" zener, like LM329 (6.9V) or LM336-5.0 (5V)?

    Nice job, Geoff!
     

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