Does BJT area related with Current?

[zahrein]

reverse saturation current bjt

Guyz,

While i was deisgning the op-amp 741 BJT using the cadence spectre, i have to put the value of the area. The values are range from 1 to 16 for a different transistor.

What is the relation with current? Is it bigger area has bigger Is(saturation current)? Or else?

Thank you

 

[flatulent]

bipolar transistor reverse saturation current

The current approximately scales wth area. Because of the voltage drop across the base region, most of the current flows on the edge of the base-emitter junction.

 

[zahrein]

current equations for bjt

Does it means the bigger the area, the higher the current (Ic)?

 

[flatulent]

bjt reverse saturation current

It means the current is larger for a given base-emitter voltage applied to the transistor.

 

[lastdance]

complete collector current equation bjt

Recall the collector current equation (Gray & Meyer)
Consider the effect on your poles as there will be a larger parasitic capacitance in the junctions. Unless you want the high current (or as multiples in Bandgap), do not use excessively big device.

 

[Vamsi Mocherla]

emitter area saturation current of bjt

Actually the Is (the reverse saturation current) depends on the area of the emitter and width of the base. In say, CMOS processes, we can play around with the areas of the emitter to get higher currents because Ic=Is.exp(VBE/Vt).

 

[lastdance]

bjt current equation

I think your equation is wrong, there should have been an area factor.

 

[rongli]

saturation current bjt

it has the option to write the device multiplier.

 

[Vamsi Mocherla]

Well the equation for the current in the bipolar device is right, the current equation in a bipolar device is given by Ic = Is .exp(VBE/Vt)

where Is = qADn ni^2/Wb Na

where q - electronic charge
A - Area of the emitter
Dn - diffusion constant for electrons
ni - Intrinsic Carrier concentration
Wb - Width of the base
Na - Acceptor Ion Concentration in the base