Using the B-E junction of a transistor as a diode

[ChrisP58]

So, the Base-Emitter junction of a BJT is essentially a diode.

My interest is purely economic. I have a circuit that uses a PNP (2N3906) that is also connected to a diode (1N4148).

I can get a dual PNP in a SOT-363 package. By using half of it for the diode, there is only one part to buy and populate.

It simulates just fine in Ltspice. But are there any non obvious potential issues with using it as such?

 

[danadak]

I was just looking at that -slope portion of Vbe curve as current is increasing,
a potential oscillator in the making.....

 

[Lightium]

I hope this don't become trend and markets adjust forcing the rest-of-us to do the same.

 

[crutschow]

I can get a dual PNP in a SOT-363 package.

Are the two transistor totally isolated from each other?

 

[ChrisP58]

Are the two transistor totally isolated from each other?

Yes. At least that is my interpretation of the phrase "two discrete devices" in the datasheet.

It has been interesting to follow this thread.

I've changed my circuit to use both parts as transistors, so will use a diode for the diode.

 

[Beau Schwabe]

To the OP - Depending on the original circuit, it "might" make a difference when using a diode vs. a transistor. For example in a current mirror circuit ...

See Simulation:

https://kit-start.com/Forum/Schematic%20Simulation%2005_24_2023.html