LED bias and differential pairs

[zigzagflux]

Have been considering using an LED to bias my Raven linestage. Normally, I see either a common cathode resistor to bias the diff pair, or a CCS. Would an LED be just as good an option?

I will require a 2V, 40 mA bias node, so I was planning on paralleling two red LED's. Yes, no ?

Thanks.

 

[SY]

An LED is exactly the opposite of what you need. It's an excellent voltage source (i.e., low source impedance) whereas what you need for a diff amp is an excellent current source/sink (i.e., high source Z).

 

[zigzagflux]

Suspected such. We shall stick with the resistor for now.
thx