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Author Topic: "RF and molecular bond breaking Kanzius style"  (Read 102626 times)

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Do you have time to redesign your circuit for the 2GHz un-buffered version of the ADL5391 IC?
No, but I have diapers and CMV ;)
Nonetheless, this needs to be done and time can always be scrounged up.
First, I'd have to buy the unbuffered chip to verify that my alterations work as intended.

I did make a Eagle CAD lib for the ADL5391 and I think it will be very difficult to hand solder the IC.
Yes, it is difficult but I had done it and so did Itsu - I was surprised when he did because people his age usually have problems with eyesight and fine motor control ...but apparently that did not apply to him.  
Our Russians friends probably would  need some vodka, because without it, the handshaking would prevent any success with soldering this puny chip.
Anyway, for low frequency experimenting, I prefer to solder this chip to a DIP8 socket and go from there...
   
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No, but I have diapers and CMV ;)
Nonetheless, this needs to be done and time can always be scrounged up.
First, I'd have to buy the unbuffered chip to verify that my alterations work as intended.
Yes, it is difficult but I had done it and so did Itsu - I was surprised when he did because people his age usually have problems with eyesight and fine motor control ...but apparently that did not apply to him.  
Our Russians friends probably would  need some vodka, because without it, the handshaking would prevent any success with soldering this puny chip.
Anyway, for low frequency experimenting, I prefer to solder this chip to a DIP8 socket and go from there...


verpies,

I have started to design a board around the PIC16F88 mcu. I plan to use RS232 to send data to a PC.
I will implement two digital variable resistors so that the offset and gain can be controlled by firm ware.
The built in A/D in the PIC is 11 bit so I plan to use an external A/D of 12 or more bits.

Thanks for taking time to look into this.

GL.
« Last Edit: 2015-06-18, 13:36:06 by Groundloop »
   

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I had to dig it out of my projects box.

First picture; the layout of the circuit how i set it up
Second picture; zoomed in on the puny chip
Third picture; on my age you need something like that.

It never worked like planned, probably because of the wrong (2GHz unbuffered) chip.


I think it still looks very promising, so please go for it.


Regards itsu
   
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I had to dig it out of my projects box.

First picture; the layout of the circuit how i set it up
Second picture; zoomed in on the puny chip
Third picture; on my age you need something like that.

It never worked like planned, probably because of the wrong (2GHz unbuffered) chip.


I think it still looks very promising, so please go for it.


Regards itsu


Itsu,

Thank you for posting your build. I plan to make 2 PCBs, one is the circuit and a small PCB for the IC that give me
a standard 16 pin DIL. That way I can get someone that are able to solder the small IC onto the DIL board. The
rest of the board uses standard easy to solder through hole components. I plan to make the PCB fit a Hammond
standard alu. box. (Hammond 1455C801BK). The circuit will have USB to get data into a PC. The USB will power
the circuit.

EDIT: Has started a project over here: http://www.overunityresearch.com/index.php?topic=3106.msg49663;topicseen#msg49663

GL.
« Last Edit: 2015-06-18, 13:35:44 by Groundloop »
   

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EDIT: Has started a project over here: http://www.overunityresearch.com/index.php?topic=3106.msg49663;topicseen#msg49663
Shit!  Now I will definitely have to scrounge up some time for it.
   

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there are solutions for that,   you will be having your hands free and the kid will be learning something   ;D

Regards Itsu
   

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there are solutions for that,   you will be having your hands free and the kid will be learning something   ;D

Regards Itsu

 ;D ;D ;D ;D ;D ;D ;D ;D........................... ;)

Ones a doddle, been there, " T shirt " etc. etc.

 O0


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Meanwhile i was running some tests on my 13.56mHz amplifier module, but allthough 150W was reachable, the efficiency stayed very low <40%.
Also the current through the driver ixdd414ci went up from 500mA at 4.5MHz to 1.8A at 13.56MHz which is out of its spec's.

I think its the driver ixdd4141ci which cannot handle this high frequency, so therefor i tested it without voltage on the drains.

Yellow is the voltage on the output of the driver / gates
blue is the input from the FG.

First screenshot is at 4.5MHz, second on 13.56MHz.

You can see that the output of the driver drops in amplitude, the signal gets distorted (more sawtooth like) and shifts in phase.
The MOSFET's will have a hard time to switch on/off hard this way causing the bad efficiency i think.

I did add an IDH12SG60C schottky diode across both drain/sources of the MOSFET's to aid the body diodes, but without improvements.

Any thoughts on this, can i improve on the gate signal in any way?
Or should i find a better driver like a DEIC420?

Regards Itsu
 
   

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Hi Itsu

have to go out and will look more later, but maybe it is the capacitance of the gate (being Two) in relation to the increase of frequency, what happens if you disconnect one? and power up slowly to voltage

back later

regards

Mike 8)


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As a general rule, the most successful person in life is the person that has the best information.
   

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First screenshot is at 4.5MHz, second on 13.56MHz.
With 0V between drain and source ?

You can see that the output of the driver drops in amplitude, the signal gets distorted (more sawtooth like) and shifts in phase.
Sawtooth waveform means that the driver is too slow and you are approaching its slew rate limit.  It does not mean that the driver is too weak (max source/sink current).
What is the driver's minimum rise time, anyway?  
Are you seeing this driver's maximum slew rate (V/ns) on the scope when there is 0V between drain and source  - as not to be bothered by the Miller effect ?

   

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From the datasheet:   

"The IXDD414 can source and sink 14A of peak current while producing voltage rise and fall times of less than 30n".

Yes.


Itsu
   

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Hi Itsu

have to go out and will look more later, but maybe it is the capacitance of the gate (being Two) in relation to the increase of frequency, what happens if you disconnect one? and power up slowly to voltage

back later

regards

Mike 8)


To answer Mikes question, the FQA11N90C MOSFET has an Ciss (input capactitance) of 2530pF typical.
So for 2 MOSFET's that means 5nF.

In the driver datasheet is a section mentioning:

"Say, for example, we are using the IXDD414 to charge a 5000pF capacitive load from 0 to 25 volts in 25ns.
 Using the formula: I= ∆V C /∆t, where ∆ V=25V C=5000pF & ∆ t=25ns we can determine that to charge 5000pF to 25 volts
 in 25ns will take a constant current of 5A.  
 (In reality, the charging current won’t be constant, and will peak somewhere around 8A)"


So that means to me that this driver should be able to drive a 5nF capacitive load (the driver is fed from a 12V battery).

Regards Itsu
   

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From the datasheet:  
"The IXDD414 can source and sink 14A of peak current while producing voltage rise and fall times of less than 30ns".
Well, then connect just a 5Ω non-inductive resistor to the output of this driver and verify that its output can really rise in 30ns - there are a lot of counterfeit chips out there nowadays with inferior characteristics.

14A means a strong driver but 30ns is not very quick

Even if the output of this driver can rise in 30ns, it probably still needs another 30ns to fall.  So the best you can do with this chip is a triangular waveform (or asymmetrical  sawtooth) with a minimum period of 60ns.
...and 60ns is the period of 16.6MHz triangular waveform.  That's pretty close to your 13.6MHz
   

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OK,  good plan, i just have to find myself a 5Ω non-inductive resistor.

But if it confirms the triangle waveform, then i really need a faster driver.


Thanks,     Itsu
   

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OK,  good plan, i just have to find myself a 5Ω non-inductive resistor.
But if it confirms the triangle waveform, then i really need a faster driver.
You can always connect several carbon resistors in parallel.

Remember that the 5Ω resitor to ground is only a sourcing load for the driver, so the rise time will be much slower than the fall time, which is not opposed by any loading resistor to VCC.
 
If you still have some of the UCC27511 drivers then note that they are fast (7ns) but to be able to meet the 14A sink current specification of IXYS you'd need to parallel 2 of them.
   

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Ok,  4x 22 Ohm parallel (5.5 Ohm) from driver output to ground.

First screenshot overall signal at 13.5MHz, looking good:
yellow: input from FG
Blue:   output from driver to ground

Next 2 screenshots are zoomed in on the rise / fall times of 4.5MHz, then 13.5MHz (look at the increased delay on 13.5MHz)
Also looking good,  the 4x 22 Ohm resistors getting hot fast.


Regards Itsu
« Last Edit: 2015-06-19, 15:10:33 by Itsu »
   

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Careful Itsu, they will get hot as the output is around 4w or more depending on voltage input.

Looks like the driver is fine, very clean, I think the problem is the mosfets or maybe (the 0.5 ohm 5w resistor if left out) @ 13.56MHZ.

Other problem could be a very bad match on the output @ 13.65MHz.

Most of these mosfets are good up to 30MHz it seems, so something around the mosfets is causing this, "SWR", check this with the swr meter you have at a lower power output (reduce the drain voltage).

Part of your dummy load could be shot with the power being put into it before!!

Not much left in the circuit to think about :-\

Regads

Mike 8)


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"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860

As a general rule, the most successful person in life is the person that has the best information.
   

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Oops,  looks like i measured on 4.5 and 13.5 KHz  instead of MHz,    need to redo those tests.......

You posted the alteration during my post :)

OK

standing by

Mike 8)


---------------------------
"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860

As a general rule, the most successful person in life is the person that has the best information.
   

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Mike,  yes,  sorry about that, i found those screenshots very clean, too clean.
Anyway,  now ones are up now, but i think looks ok still.

Guess you are right,  probably a bad mismatch in the output which reflects back on the input (driver).  
By the way, i have 2x 0.1 Ohm resistors in the gate lines one for each MOSFET
 
Itsu
   

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Next test with only 1 MOSFET attached,  no drain voltage applied.

Again yellow input FG, blue gate signal.  first on 4.5MHz,  then on 13.5MHz.
So we see a dramatic difference compared with the signals of only the 5.5 Ohm resistor attached.

Regards Itsu
   

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Mike,  yes,  sorry about that, i found those screenshots very clean, too clean.
Anyway,  now ones are up now, but i think looks ok still.

Guess you are right,  probably a bad mismatch in the output which reflects back on the input (driver).  
By the way, i have 2x 0.1 Ohm resistors in the gate lines one for each MOSFET
 
Itsu

OK on the resistors, better safe than sorry. Try checking the SWR with lower power which your meter can take, make up a 10w 50 ohm load if you can O0

regards

Mike 8)


---------------------------
"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860

As a general rule, the most successful person in life is the person that has the best information.
   

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Next test with only 1 MOSFET attached,  no drain voltage applied.

Again yellow input FG, blue gate signal.  first on 4.5MHz,  then on 13.5MHz.
So we see a dramatic difference compared with the signals of only the 5.5 Ohm resistor attached.

Regards Itsu

Looks like mosfet problem at 13.56MHz

Do you have another mosfet? if so try one

regards

Mike 8)


---------------------------
"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860

As a general rule, the most successful person in life is the person that has the best information.
   

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This is same test as above, but now with 2 MOSFETs attached,  no drain voltage applied  (no output module attched either).

4.5MHz stays ok,  13.5MHz gets even worse:

So it looks to me that the driver should be ok on 13.5MHz,  but somehow the MOSFETs (capacitance?) cause the driver to misbehave.

Regards Itsu
   

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Dear Itsu.

Am I being daft?
Your second screen shot reads over 60 MHz!! Well that's what your scope says.

Cheers Grum.


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I think the mosfet is no good for the higher 3X frequency or they are damaged from before, though the 4.5 signal seems OK, so, can't take the higher frequency without breaking down internally it seems.

regards

Mike 8)


---------------------------
"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident."
Arthur Schopenhauer, Philosopher, 1788-1860

As a general rule, the most successful person in life is the person that has the best information.
   
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