# Current Source in BJT Model from HSPICE

#### miezko

Joined Nov 18, 2013
3
Hello,

(Title should be: "Current Source in BJT Model from HSPICE")

I'm trying to implement the BJT model from the HSPICE Manual (see page 146 at http://www.ece.rochester.edu/courses/ECE222/hspice/hspice_devmod.pdf) in another circuit simulator. This model includes the collector emitter current source but no explicite base current source. When I check the DC model equations however (page 156), they give two formulas, one for the collector current ic and one for the base current ib.

Is this an error in the manual? Where should I place the ib current source in the schematic?

Thanks in advance and best regards,
Miezko

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#### LvW

Joined Jun 13, 2013
1,749
.........
This model includes the collector emitter current source but no explicite base current source. When I check the DC model equations however (page 156), they give two formulas, one for the collector current ic and one for the base current ib.
Is this an error in the manual? Where should I place the ib current source in the schematic?
No - it is certainly not an error.
May I ask you why do you expect a current source for Ib?
Ib is just a result of an applied voltage Vbe - and as such it is modelled in any SPICE simulator.
Note that the bipolar transistor in fact is a voltage controlled (non-ideal) current source. And all the models are built correspondingly.

#### miezko

Joined Nov 18, 2013
3
Hi,

Thank you for your answer! I was confused since this formula is not used for any other calculation.

Gives the formula for ic (page 152) the current value for the current source "ice" or is this the terminal current (directly flowing in the collector node)?

#### miezko

Joined Nov 18, 2013
3
Hey, I just wanted to ask again about the current source ice. There is one formula for ic on page 152 but there is no formula for ice. In the manual it is written:

ic = External collector terminal current
ice = DC current collector to emitter

So what is the correct formula for ice in the schematic (page 146)?

Thanks in advance for any help