J

#### Jon Kirwan

- Jan 1, 1970

- 0

have posted it here.

....

I recently looked at the general schematic for the LM334 on National's

datasheet and with a quick sweep of my arms came up with a design

Iset/Ibias of 8, not 16 as they show on page 5. I'm off by a factor

of two.

My logic went like this. 1/2 of the I from V+ flows via Q6 to the R

rail. 1/4 via Q4 and 1/4 via Q5. Q5's 1/4*I flows via Q1 to the R

rail, too. So now up to 3/4*I into the R rail. Q4's 1/4*I passes

through two paths. The Ic(Q2)=Ic(Q1)/2... but Ic(Q1)=1/4*I, so that

is 1/8*I, leaving the other 1/8*I for Q3's Vbe conduction, which also

flows to the R rail. So the R rail gets 7/8*I and the V- picks up

1/8*I. Multiplying through by 8 to get rid of the divisor, I see a

factor of 8 for Iset/Ibias... not 16.

Can someone do a quick description about how to arrive at something

more like 16 from the schematic? I'm missing a clue (or two.)

To be handy, here's the sheet:

http://www.national.com/ds/LM/LM134.pdf

Thanks in advance,

Jon