How's about a Depletion Mode / Enhancement Mode CCCS

MIKET · 11th September 2003, 01:29 AM

I have some DN2540's and IRF 510's and have been considering using the DN2540 on the supply side and the IRF510 on the tube side. Any thoughts?

Bandersnatch · 11th September 2003, 03:14 AM

Hey-Hey!!!,
If you use the enhancement mode, you will need bateries. Use the depletion mode and you cna get away without, though it is beter to use them on the bottom ones anyway...
regards,
Douglas
ps. don't let me stop you from trying something

EC8010 · 11th September 2003, 11:58 AM

This might be useful for the DN2450. Top curve is -1.5V, and the curves go progressively more negative at 0.1V per curve.

Bas Horneman · 11th September 2003, 01:07 PM

Hi EC8010,

How is this graph useful? Because I would like it to be!

Regards,
Bas

EC8010 · 11th September 2003, 01:20 PM

Because you can use it in the same way that you use pentode curves to determine the required resistance for a particular current.

Vertical axis: Ids
Horizontal axis: Vds

Suppose that you wanted to pass 9mA. Looking at that current, you find that the second curve down is pretty well 9mA, and it achieves this with Vgs = -1.6V. If you put a resistor in the source circuit of 1.6/0.009 = 178R, and connect the gate to the bottom of that resistor, you have created a 9mA two-terminal CCS.

Additionally, the curves show the minimum voltage required across the device (Vds) for it to achieve a constant (high) output resistance.

Bas Horneman · 11th September 2003, 02:06 PM

9mA achieved with -1,6v.. so where does that put you on the graph..i.e. where is the operating point?

Quote:

Additionally, the curves show the minimum voltage required across the device (Vds) for it to achieve a constant (high) output resistance.

Where is resistance on the chart?

I mean..how does one see that? Left of the dotted line?

EC8010 · 11th September 2003, 02:41 PM

Resistance is inversely proportional to the slope of the curves. A perfectly horizontal curve has slope = 0, and implies infinite resistance. For best CCS operation, you want to avoid operating where the curve deviates from horizontal, so at higher currents, you need a higher Vds to stay on the horizontal part.

EC8010 · 11th September 2003, 02:57 PM

Your operating point is somewhere along the 1.6V line. If you were using the CCS in the cathode circuit of a valve, and the grid was grounded, then the cathode might be at 8V, so that would place the operating point at 8V less the 1.6V drop across the source resistor = 6.4V, which is well to the right of the curved region.

Bas Horneman · 11th September 2003, 03:12 PM

Thanks

EC8010 · 11th September 2003, 03:44 PM

You're welcome.

11th September 2003, 01:29 AM	#1
MIKET diyAudio Member Join Date: Jul 2003 Location: Maine	How's about a Depletion Mode / Enhancement Mode CCCS I have some DN2540's and IRF 510's and have been considering using the DN2540 on the supply side and the IRF510 on the tube side. Any thoughts?

11th September 2003, 03:14 AM	#2
Bandersnatch diyAudio Member Join Date: Jul 2003 Location: Ann Arbor, MI	Hey-Hey!!!, If you use the enhancement mode, you will need bateries. Use the depletion mode and you cna get away without, though it is beter to use them on the bottom ones anyway... regards, Douglas ps. don't let me stop you from trying something __________________ the Tnuctipun will return

11th September 2003, 01:20 PM	#5
EC8010 diyAudio Moderator Join Date: Jan 2003 Location: Near London. UK	Because you can use it in the same way that you use pentode curves to determine the required resistance for a particular current. Vertical axis: Ids Horizontal axis: Vds Suppose that you wanted to pass 9mA. Looking at that current, you find that the second curve down is pretty well 9mA, and it achieves this with Vgs = -1.6V. If you put a resistor in the source circuit of 1.6/0.009 = 178R, and connect the gate to the bottom of that resistor, you have created a 9mA two-terminal CCS. Additionally, the curves show the minimum voltage required across the device (Vds) for it to achieve a constant (high) output resistance. __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

11th September 2003, 02:41 PM	#7
EC8010 diyAudio Moderator Join Date: Jan 2003 Location: Near London. UK	Resistance Resistance is inversely proportional to the slope of the curves. A perfectly horizontal curve has slope = 0, and implies infinite resistance. For best CCS operation, you want to avoid operating where the curve deviates from horizontal, so at higher currents, you need a higher Vds to stay on the horizontal part. __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

11th September 2003, 02:57 PM	#8
EC8010 diyAudio Moderator Join Date: Jan 2003 Location: Near London. UK	Operating point Your operating point is somewhere along the 1.6V line. If you were using the CCS in the cathode circuit of a valve, and the grid was grounded, then the cathode might be at 8V, so that would place the operating point at 8V less the 1.6V drop across the source resistor = 6.4V, which is well to the right of the curved region. __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

11th September 2003, 01:07 PM	#4
Bas Horneman diyAudio Moderator Emeritus Join Date: Apr 2002 Location: The Netherlands Blog Entries: 18	Hi EC8010, How is this graph useful? Because I would like it to be! Regards, Bas

11th September 2003, 03:12 PM	#9
Bas Horneman diyAudio Moderator Emeritus Join Date: Apr 2002 Location: The Netherlands Blog Entries: 18	Thanks __________________ Boatanchor amps forum My "adventures" in audio

11th September 2003, 03:44 PM	#10
EC8010 diyAudio Moderator Join Date: Jan 2003 Location: Near London. UK	You're welcome. __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

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