Vbe Multiplier Somebody Smart Please Help

[mefistofelez]

I do not know if this is the proper place to post this, but anyway:

I have been trying to understand PMA’s amplifier introduced here: http://www.diyaudio.com/forums/show...0543&highlight=

I have a problem with a Vbe multiplier disclosed by Nelson Pass in his patent: US3,995,228. To achieve bias voltage Vb = 9 V, with 2*Vbe = 2.8 V, the equation to be solved is:

(R1+R2+R3)/R2 = Vb/2*Vbe

Setting R1=R3= 600 Ohm, R2 = 543 Ohm

Looking at the schematics: http://web.telecom.cz/macura/pm_ab_er1.gif , the resistor R7 - corresponding to R2 - is 10 kOhm.

Now, interestingly enough, simulation confirms the value 10kOhm.

Any help would be appreciated.

M

 

[peranders]

PMA's circuit is an error correction circuit also, not exactly a Vbe multiplier.

 

[mefistofelez]

Dear Per,

I do understand that. But the function of the curcuit is based on the Vbe multiplier from Nelson Pass' patent, see, Q1, Q2, D1, D2, R8, R9, R10, and R11.

This is, what I am trying to understand.

M

 

[peranders]

If you want to understand this circuit you can apply "DC" and two levels and than calculate voltages and currents.

Put in + 1 volts, +10 vots and don't forget to add a load at the output. If you have these two values I'm sure you can get a picture of the problem.

If you are lazy you could also put this (maybe) simplfied circuit into LTSpice and simulate it.