diode voltage in junction

[sharma46]

can we test junction voltage of a diode when no supply is given

 

[cameo_2007]

yes, but by using a multimeter.

 

[TonyM]

No, you need to pass a reasonable current through the diode and measure the voltage drop.

A 'reasonable' amount of current depends upon the device characteristics - refer to the I/V curve in its data sheet.

 

[cameo_2007]

Any multimeter which has the "Diode" test mode will have the capability to source a reasonable amount of current.

 

[TonyM]

No, you need to pass a reasonable current through the diode and measure the voltage drop.

A 'reasonable' amount of current depends upon the device characteristics - refer to the I/V curve in its data sheet.

Actually, when you say 'a diode when no supply is given', I first took it you meant a diode component in your hand. If it's in circuit on a board, you have to be careful of the loading effects of other parallel circuitry spoiling your measurement. This includes the supply rails which often have a very low impedance when the circuit is powered off (depends on your PSU). Beware of this when you use a multimeter etc across a diode in circuit.

 

[dean_winchester]

Mulitmeter has a diode test mode. That can be used. Or simply plug in the Power supply and a resistance in series to Diode.
Now, using multimeter you can measure the variation also.