Matching Diodes...

[LyleCaldwell]

I need some diodes with a forward current of 600ma.  Do I need to order a whole bunch and then match them or is there a source for diodes with tight tolerances?  The diode shown in the 78xx datasheet is a 1N4148, but looking at its datasheet it shows a forward current of 150ma.

I'm using the diode in question on pin 2 of a 7809 to get an output of 9.6vdc.

[Paul Perry (Frostwave)]

The thing is, diodes have a different foward current at different voltages. I don't know what current is goingto be flowing thru the ground pin that you are trying to jackup.. something pretty low I bet... Isuggest trying 1, 2 and even 3 diodes in series on the leg to ground & seeing what happens, under whatever load you are driving.
I can't thinkof many places where 600mV on a power rail is going to matter, anyway!

[cd]

FAR easier to get yourself an LM317 and a trimpot, and trim it down to whatever precise voltage you need.

[brett]

Hi.
Your application doesn't need close matching. 
But instead of 1N4148s, use a 1N4001/4/7.  They'll handle a fair bit of continmuous current and heat (about 1 amp and 1W, I think), and a lot more on a low duty cycle (around 10 amps at 2% duty in a couple of circuits where I use them).
cheers

[amz-fx]

I'm using the diode in question on pin 2 of a 7809 to get an output of 9.6vdc.

You don't need to worry about selecting the device...  but if it is a 7809 then you probably need a 1N4001 to handle the max current (to be safe).

regards, Jack

[LyleCaldwell]

Thanks all - I went ahead and switched to an LM317.