Rectifier Foward Voltage?

Troncones · 18th September 2011, 04:05 PM

Eli made a statement about a rectifier having a lower foward (on) voltage. I can't find my way back to the thread it was in. I have looked at several data sheets for rectifiers and haven't spotted it.

Where can this info be found?

When calculating PS ripple where does this data fit in?

DF96 · 18th September 2011, 04:43 PM

It may be given in graphical form: voltage vs current.

It only has a small effect on PSU ripple. The main issue is current drawn vs. reservoir cap value, then any smoothing which follows.

cogsncogs · 18th September 2011, 09:27 PM

Some data sheets, like one for a RCA 5V3A, will have it under
Typical Operation:
AC Plate to Plate Supply Voltage
and so forth...
Characteristics: Tube-Voltage Drop for plate mA. = 350mA
Per Plate.....................42 volts

Some data sheets will have listed as such, others will be as DF96 stated in graphical form or both.

SemperFi · 18th September 2011, 09:45 PM

Isn't rectifier's plate resistance pretty constant within it's operating limits? So if the datasheets say it drops 20volts @ 100mA the plate resistance is 200ohms, and you can then calculate the voltage drop at other load currents.

payitforwardeddie · 18th September 2011, 09:48 PM

Quote:

Originally Posted by SemperFi

Isn't rectifier's plate resistance pretty constant within it's operating limits? So if the datasheets say it drops 20volts @ 100mA the plate resistance is 200ohms, and you can then calculate the voltage drop at other load currents.

Its not that linear. Check out the graph on page 5 on this link for the GZ34. http://www.r-type.org/pdfs/gz34.pdf

DF96 · 18th September 2011, 09:55 PM

An ideal thermionic diode will have a 3/2 power law, so I~V^(3/2). Real diodes follow this law only approximately.

Miles Prower · 19th September 2011, 04:09 AM

Quote:

Originally Posted by Troncones

Eli made a statement about a rectifier having a lower foward (on) voltage. I can't find my way back to the thread it was in. I have looked at several data sheets for rectifiers and haven't spotted it.

Where can this info be found?

Spec sheets, and the plate characteristics as shown here. (attached) What they're calling "plate voltage" is really plate-to-cathode voltage, and therefore, forward voltage.

Quote:

When calculating PS ripple where does this data fit in?

It doesn't.

Troncones · 22nd September 2011, 02:59 PM

Thanks Everybody

18th September 2011, 04:05 PM	#1
Troncones diyAudio Member Join Date: Dec 2009 Location: Orange County, California.	Rectifier Foward Voltage? Eli made a statement about a rectifier having a lower foward (on) voltage. I can't find my way back to the thread it was in. I have looked at several data sheets for rectifiers and haven't spotted it. Where can this info be found? When calculating PS ripple where does this data fit in? __________________ The Myth: A hand full of Tubes, Caps, Resistors and Iron and you have an Amp. The Reality: You have self induced Dementia. Newbie.

22nd September 2011, 02:59 PM	#8
Troncones diyAudio Member Join Date: Dec 2009 Location: Orange County, California.	Thanks Everybody __________________ The Myth: A hand full of Tubes, Caps, Resistors and Iron and you have an Amp. The Reality: You have self induced Dementia. Newbie.

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18th September 2011, 04:43 PM	#2
DF96 diyAudio Member Join Date: May 2007	It may be given in graphical form: voltage vs current. It only has a small effect on PSU ripple. The main issue is current drawn vs. reservoir cap value, then any smoothing which follows.

18th September 2011, 09:27 PM	#3
cogsncogs diyAudio Member Join Date: Jul 2003 Location: Wayne, West Virginia	Some data sheets, like one for a RCA 5V3A, will have it under Typical Operation: AC Plate to Plate Supply Voltage and so forth... Characteristics: Tube-Voltage Drop for plate mA. = 350mA Per Plate.....................42 volts Some data sheets will have listed as such, others will be as DF96 stated in graphical form or both.

18th September 2011, 09:45 PM	#4
SemperFi diyAudio Member Join Date: Jan 2002 Location: nowhere	Isn't rectifier's plate resistance pretty constant within it's operating limits? So if the datasheets say it drops 20volts @ 100mA the plate resistance is 200ohms, and you can then calculate the voltage drop at other load currents.

18th September 2011, 09:55 PM	#6
DF96 diyAudio Member Join Date: May 2007	An ideal thermionic diode will have a 3/2 power law, so I~V^(3/2). Real diodes follow this law only approximately.

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