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-   -   Juma's Easy-Peasy Capacitance Multiplier (https://www.diyaudio.com/forums/power-supplies/297921-jumas-easy-peasy-capacitance-multiplier.html)

Mooly 13th October 2016 06:53 PM

3 Attachment(s)
As Mark said really, a logic level low Rds device. This is the PSMN1R025YLD.

Looks good ;)

Ripple at 1.7 amps steady state and pulsed 1.7 amp.

I've attached the spice file set up for the IRF240 which will run straight off in LT IV. The PSMN1R025YLD FET model might only be available in LT XVII

xrk971 13th October 2016 07:16 PM

That PSMN1R025YLD looks like an awesome FET, however it has 25v limit which sort of limits it to 15v class A head amps or maybe preamps. A 25v typical class A supply might be too much. I like the 890 microOhm Rs_on, and continuous 100A!

This could be a very useful little FET to make a cap multiplier for my F5 head amp.

http://datasheet.octopart.com/PSMN1R...t-62336464.pdf

Is the input capacitance too large to use it as an audio OPS?

Mooly 13th October 2016 07:49 PM

The capacitance shouldn't be much of a problem at audio frequencies, and these things are meant to be used at high speeds in DC/DC convertors and so on.

Wouldn't like to say just how suitable it would be overall though but it could make for an interesting project. Maybe there are other higher voltage devices available in a similar series of parts.

xrk971 13th October 2016 08:00 PM

For $1.70ea I might buy a few to play with, if not for cap multiplier, then maybe as OPS. The high capacitance will require a low impedance driver though.

Mooly 13th October 2016 08:16 PM

The driver has to be able to both charge and discharge the gate capacitance and so a few milliamps need to be available.

xrk971 13th October 2016 08:23 PM

Quote:

Originally Posted by Mooly (https://www.diyaudio.com/forums/power-supplies/297921-jumas-easy-peasy-capacitance-multiplier-post4855795.html#post4855795)
The driver has to be able to both charge and discharge the gate capacitance and so a few milliamps need to be available.

Perhaps something like this could be done for a small amp to drive headphones but replace the IRF610 with this unit (assuming there is a complementary p-channel)?

Another Juma creation:
https://www.diyaudio.com/forums/atta...a-f5-bjtin.gif

jkuetemann 13th October 2016 10:44 PM

Quote:

Originally Posted by xrk971 (https://www.diyaudio.com/forums/power-supplies/297921-jumas-easy-peasy-capacitance-multiplier-post4855641.html#post4855641)
Thanks, Jason. I don't know enough to understand why it has so many transistors though - are there added benefits like lower dripeout voltage or better ripple control vs the Juma "Easy Peasy" circuit? I submit, the Juma circuit is dead simple, still.

You grabbed the schematic from post #1, not the final version in post #65. You won't like it though since it is more complicated yet again ;).

Lower 'drop-out' is possible with normal Vgs devices since they operate common source rather than as a follower. Two pole filtering reduces ripple a fair bit over the usual single pole.

Juma's arrangement is a pretty classic implementation.

Mooly 14th October 2016 07:47 AM

Quote:

Originally Posted by xrk971 (https://www.diyaudio.com/forums/power-supplies/297921-jumas-easy-peasy-capacitance-multiplier-post4855801.html#post4855801)
Perhaps something like this could be done for a small amp to drive headphones but replace the IRF610 with this unit (assuming there is a complementary p-channel)?

I don't see why not although as always, it would be advisable to do some real measurements and weigh up the pros and cons compared to more traditional devices.

xrk971 14th October 2016 08:21 AM

I just ran some sims in TINA and see that this cap multiplier can really save one some money with the cost of big caps. For example, if I simply removed my CRC consisting of a 33mF//0.12R//33mF and replaced it with a single 33mF and then couple that to the cap multiplier - it still works well with probably 100uV ripple with a 2amp steady load. So right there, one can eliminate qnty 4 x 33mF caps in a class A PSU. That's a significant savings in money and volume needed inside the case.

sgrossklass 14th October 2016 08:50 AM

Guess why people like cap multipliers in this application...

Just be careful not to optimize dropout voltage too much, or otherwise it might drop out of regulation given high input ripple. Less of a problem with MOSFETs, more so with BJTs.


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