Any clue of how to use this part as a current sink for a CF? - diyAudio
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Old 31st July 2004, 01:29 PM   #1
G is offline G  United States
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Default Any clue of how to use this part as a current sink for a CF?

I've asked questions about this before about how to use it as a plate load. How would you use it as a current sink? Would you place a resistor above the "A" terminal and connect the "G" terminal to the top of the resistor?

http://www.ixys.com/98704.pdf
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Old 31st July 2004, 01:48 PM   #2
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Quote:

How would you use it as a current sink? Would you place a resistor above the "A" terminal and connect the "G" terminal to the top of the resistor?


No, don't use a resistor at the A. In fact you can use it as a sink just like the diagram in the PDF data. just connect the resistor (eg 100 Ohms for 25mA) from K to ground, connect G to ground, and connect the circuit you want to take a constant current FROM - to the A terminal.

Be sure to heatsink the device adequately to dissipate I(mA)*(Vdrop from A to K) in mW.

Take care if you are experimenting with a current source in a valve cathode circuit, since if it goes open-circuit you will get a big voltage between the two points going to A and K & A and G.
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Old 31st July 2004, 02:47 PM   #3
DougL is offline DougL  United States
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Quote:
How would you use it as a current sink?
If you use figure 1, attach the Tubes cathode to A.
ground G and place the resistor K to Ground.
for 15 ma, the resistor appears to be about 200 ohms.
Basically looks a bit like a triode from a bias standpoint.
put negitive voltage on the K pin and ground the input, G.
AC is very like a pentode, BTW.

Important notes, indirectly heated triodes only. Directly heated triodes need a more complex treatment.

By the way, nice part. with 350v max, I bet its not cheap.

Doug
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Old 31st July 2004, 03:17 PM   #4
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Using it as a plate load, you connect pin A to your B+ supply, and the bottom part where G and Rk meet, to the tube's anode. The amplified signal is also taken from this last point.

Note that the min dynamic resistnace is 10k, if you need more, it is better either to take a normal resistors or a real (discrete) current source. Also, the dynamic resistance can vary VERY wildly, so unless you have soem gain-stabilising feedback in your amp, it's gain will also vary all over the place.

Jan Didden
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Old 31st July 2004, 05:00 PM   #5
G is offline G  United States
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Quote:
Originally posted by janneman
Using it as a plate load, you connect pin A to your B+ supply, and the bottom part where G and Rk meet, to the tube's anode. The amplified signal is also taken from this last point.

Note that the min dynamic resistnace is 10k, if you need more, it is better either to take a normal resistors or a real (discrete) current source. Also, the dynamic resistance can vary VERY wildly, so unless you have soem gain-stabilising feedback in your amp, it's gain will also vary all over the place.

Jan Didden
Actually I believe Peter Millett said something, in his article about this IC, about the 10K figure being a typo and the dynamic resistance is actually 100K. Thanks for the responses.
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Old 3rd August 2004, 06:35 PM   #6
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Hi G

It looks like they corrected the data sheet. It now shows a minimum value of 160K at ~10ma.


I have measured one of the 10M45S parts in my CCS test setup. It performed very well for a single part CCS. It's performance was almost 10X better than the single Supertex DN2540. A cascade pair of DN2540's is a whole different story with very good performance. Having only one of the 10M45S parts I haven't been able to try cascading them.

You can look at the graphs of CCS measurments made to date on my webpage. Look in the CCS measurments section.

Gary
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Old 4th August 2004, 10:37 PM   #7
G is offline G  United States
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Quote:
Originally posted by Gary P
Hi G

It looks like they corrected the data sheet. It now shows a minimum value of 160K at ~10ma.


I have measured one of the 10M45S parts in my CCS test setup. It performed very well for a single part CCS. It's performance was almost 10X better than the single Supertex DN2540. A cascade pair of DN2540's is a whole different story with very good performance. Having only one of the 10M45S parts I haven't been able to try cascading them.

You can look at the graphs of CCS measurments made to date on my webpage. Look in the CCS measurments section.

Gary
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Thank you Gary. They will do for a $1.50 part. Especially for a low current preamp circuit. Thanks again.
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Old 5th August 2004, 12:30 AM   #8
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I'm using the 10M45S part to set current for my VR tubes. So far, so good.
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Old 5th August 2004, 01:34 PM   #9
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Hi,

Does anyone know if these devices are available in The Netherlands ?

I checked the IXYS website, found some european distributors, but sales are from 50 pcs. upwards...

I just need a few to try out...

Anyone?
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Old 21st September 2004, 01:14 AM   #10
DWong is offline DWong  Hong Kong
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Has anyone tried cascading the 10M45S yet? I am very interested to try but I don't know how to implement it.
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