Simple Class-A BJT Concept Amplifier (White Buffer?)

[mr_zener]

Your scheme is very similar to the one described in patent US6434243. Perhaps the information provided in the patent will allow you to improve the parameters
View attachment 1338195

So the job of D3 is to make sure T2 (and T1) are always in a conductive state?

 

[UR5FFR]

I think D3T2 works as a current mirror. You can replace D3 with a bjt-transistor with base-collector connected together.
This circuit is quite easy to calculate. Let's assume that R1=R2. Let I0 be the current through T1T2. Then for transistor T2
I0*R2 = I0*R1 = I*R3
for transistor T1
I0*R1 + I*R4 = V(D1) = 0.65
If we set the value of resistors R1R2 and some value of current I, then we can clearly determine the values of resistors R3R4
R3 = I0*R1/I
R4 = (0.65 - I0*R1)/I
Of course, this is a rather rough calculation, but it is simple and clear 🙂

 

[mr_zener]

Of course, this is a rather rough calculation, but it is simple and clear

Nope, I'm still lost. this is where I've got too now but no way its right..