Register to reply

Wrong measuring of diode I-V curve in pulsed mode

by simazPHYS
Tags: diode, i-v, pulse, resistor
Share this thread:
Jan24-12, 11:35 AM
P: 3
Hi. In order to measure the I-V curve of a normal diode in pulsed mode, I set up the following experimental kit. The experimental results do not change with pulsewidth, which is quite long (us regime), and low frequency (200hz and less).
An HP pulse generator is connected via BNC cable to an oscilloscope (1MOhm input) to measure the input voltage, and to the series of the diode under investigation and a 50Ohm resistor. The voltage drop across this resistor is measured via the second channel of the scope. No terminators are used.
The problem is that the I-V I obtain is different from what it should be (using the curve tracer or the datasheet). However, when I replace the diode with a resistor (for instance a 550Ohm resistance), the I-V I obtain is reasonably good (straigh line, ~500Ohm slope obtained).
I cannot figure out what is wrong
I can post the graphs and the photo of the experiment if necessary.
Here is the schematics

diode | 50 Ohm


Phys.Org News Partner Engineering news on
Lawsuits challenge US drone, model aircraft rules
CU-Boulder leads international unmanned aircraft testing event at Pawnee Grassland
Gesture-controlled, autonomous vehicles may be valuable helpers in logistics and trans-shipment centers
Jan24-12, 09:15 PM
Sci Advisor
P: 4,030
When you do it like that, the current flowing is that of the diode plus the resistor across the input voltage.

This will be different to that of the diode alone. It will be more like a resistor when the diode is conducting, so you will get a sloping line instead of a vertical one.

To minimise this effect, you could try putting in just a 1 ohm resistor instead of the 500 ohm one.

You can then read the voltage across the resistor as milliamps. 10 mV = 10 mA

Register to reply

Related Discussions
Measuring the Optical Power of a Pulsed Source Classical Physics 4
Pulsed laser diode driver - how it works? Electrical Engineering 4
Measuring the Boltmann constant by the IV curve of a diode Atomic, Solid State, Comp. Physics 4
IV curve of a BD-5 tunnel diode Electrical Engineering 4
How does Switch mode power supplies differ from diode rectification Electrical Engineering 3