Voltage Drop across 1N5817 Diode

H

Hans Maier

Guest
I use a 1N5817 Schottky Diode in my circuit.
According to the datasheed its forward voltage
drop should be around 0.3-0.4 V

But when i measure the voltage drop in my circuit
it is almost 1 V at 200 mA.

Did they send wrong diodes to me or am I missing
something ?

I need a diode which has a VERY low voltage drop
@about 200mA.
 
Hans Maier wrote:
I use a 1N5817 Schottky Diode in my circuit.
According to the datasheed its forward voltage
drop should be around 0.3-0.4 V

But when i measure the voltage drop in my circuit
it is almost 1 V at 200 mA.

Did they send wrong diodes to me or am I missing
something ?

I need a diode which has a VERY low voltage drop
@about 200mA.
Click to expand...
That sure sounds like a different diode. A 1N4148, perhaps.

How much reverse voltage capability do you need and how much reverse
current can you tolerate?. There are some very low voltage Schottkys
that have exceptionally low forward drop.

--
John Popelish
 
That sure sounds like a different diode. A 1N4148, perhaps.

How much reverse voltage capability do you need and how much reverse
current can you tolerate?. There are some very low voltage Schottkys
that have exceptionally low forward drop.
Click to expand...
Thanks, I will order new ones from a different supplier.
I actually don't care about reverse current as long as it
is still a diode :)

The diode has to block 5V DC and it shouldn't drop any voltage
in the other direction (idealy)... speed is not important at all.

200-300 mA should be no problem for the diode ...
 
Hans Maier wrote:
That sure sounds like a different diode. A 1N4148, perhaps.

How much reverse voltage capability do you need and how much reverse
current can you tolerate?. There are some very low voltage Schottkys
that have exceptionally low forward drop.

Thanks, I will order new ones from a different supplier.
I actually don't care about reverse current as long as it
is still a diode :)

The diode has to block 5V DC and it shouldn't drop any voltage
in the other direction (idealy)... speed is not important at all.

200-300 mA should be no problem for the diode ...
Click to expand...
If you can use surface mount parts, International Rectifier makes a 1
amp 15 volt SMB unit that drops .34 volts at 1 amp, just over .2 volt
at 200 ma.
http://www.irf.com/product-info/datasheets/data/10bq15.pdf

Here is the datasheet for the 1N5817 that shows the expected forward
drop at 200 ma of .25 volts.
http://www.diodes.com/datasheets/ds23001.pdf

--
John Popelish
 
If you can use surface mount parts, International Rectifier makes a 1
amp 15 volt SMB unit that drops .34 volts at 1 amp, just over .2 volt
at 200 ma.
Click to expand...
No, SMD is currently not an option for me.

Here is the datasheet for the 1N5817 that shows the expected forward
drop at 200 ma of .25 volts.
http://www.diodes.com/datasheets/ds23001.pdf
Click to expand...
Thanks, I hope the next diodes I get will really be 1N5817 :)
 
Hans Maier wrote:

I use a 1N5817 Schottky Diode in my circuit.
According to the datasheed its forward voltage
drop should be around 0.3-0.4 V

But when i measure the voltage drop in my circuit
it is almost 1 V at 200 mA.

Did they send wrong diodes to me or am I missing
something ?

I need a diode which has a VERY low voltage drop
@about 200mA.
Click to expand...
It's possible to get fooled with these Schottky things. If you're using
them as rectifiers in a transformer circuit, you have to remember that the
current is in the form of short pulses of much higher current than the
average current. In order to get the expected voltage drop in the
rectifier, you have to base it on the peak current. Average cuarrent is ok
when thinking about power dissipation in the device.

Neil
 
It's possible to get fooled with these Schottky things. If you're using
them as rectifiers in a transformer circuit, you have to remember that the
current is in the form of short pulses of much higher current than the
average current. In order to get the expected voltage drop in the
rectifier, you have to base it on the peak current. Average cuarrent is ok
when thinking about power dissipation in the device.
Click to expand...
Thanks Neil,

but its only used to prevent current flow from one circuit area
to another but allow it in the other direction. Absolutely rock
stable DC.
 
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