Current Regulator Diode newb question

[Lavcat]

I am wanting to use a Central Semiconductor 1N5314 4.7 ma Current Regulator Diode. My understanding is that a CRD is a jfet and a resistor in series in the same package.

My question (and I feel rather silly to ask) is about the cathode marking on the device. Does the cathode of a CRD get connected to the negative leg of the circuit for normal operation, or is there some notion of reverse bias in analogy to a zener that would mean one really wants to connect the cathode to the positive leg? I would hope it is the former, but I thought safer to ask. The device datasheet I saw is little help.

Thanks.

[jackinnj]

While you're trying to figure it out, be sure to check Walt Jung's website and this 2 part series of articles: http://waltjung.org/PDFs/Sources_101_P2.pdf

[Lavcat]

Originally Posted by jackinnj

While you're trying to figure it out, be sure to check Walt Jung's website and this 2 part series of articles: http://waltjung.org/PDFs/Sources_101_P2.pdf

Already read that thanks (at least I had read the first part).

[MRupp]

Should be normal order, so cathode as the negative pole. Zeners are really the exception in that they operate as Zeners in reverse polarity (and as normal diodes when not reversed).

Good to see that current diodes are still being made, I though they had become obsolete (like the J500 series for example).

[davidsrsb]

Usually there is no resistor. These things are ordinary n channel jfets with gate connected to source. Current value is by device sorting during production

[CopperTop]

Originally Posted by davidsrsb

Usually there is no resistor. These things are ordinary n channel jfets with gate connected to source. Current value is by device sorting during production

Although according to Current sources & voltage references - Linden T. Harrison - Google Books the current regulator diode is more than just an ordinary JFET, having superior characteristics as a current regulator. (I'd paste some of the text here, but I don't seem to be able to do it).

[davidsrsb]

It's true that using a higher current jfet and selecting a resistor between gate and source does improve the slope resistance and the temperature coefficient

[Lavcat]

Originally Posted by MRupp

Should be normal order, so cathode as the negative pole. Zeners are really the exception in that they operate as Zeners in reverse polarity (and as normal diodes when not reversed).

Good to see that current diodes are still being made, I though they had become obsolete (like the J500 series for example).

Mouser has stock of the Central Semiconductor parts although there are not a lot of values to choose from. I also just found a Central Semiconductor app note that answered my original question: "The drain becomes the anode, and the source becomes the cathode."

[Lavcat]

Originally Posted by CopperTop

Although according to Current sources & voltage references - Linden T. Harrison - Google Books the current regulator diode is more than just an ordinary JFET, having superior characteristics as a current regulator. (I'd paste some of the text here, but I don't seem to be able to do it).

Thank you for the link. I found it very useful.

Indeed, the cathode marked leg of the device really does go to the negative leg of the circuit! My application is to bias a pair of OPA627's (following a DAC) into class A. I wired the CRD's tonight and was delighted everything worked the first time and all the smoke stayed in. My eyesight is not what it once was and soldering the CRD's between the DIP pins was quite exciting.

So far the sound is good, though I must say the sound was good before. At least the CRD's have not hurt the sonics and have possibly made the performance even better.

[magnoman]

Dont forget to take them off .....