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# what is the magic voltage of a circuit??

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#### e_fever_l

##### Newbie level 4
1---what is the magic voltage of a circuit??
2---what is lambda in npn and pnp circuit??
thanks...

Hi, a far as I remember the magic voltage is for a process and techonology.
It refers to the reference voltage you would get out of a BGR you have designed in that techonology and mid it it would vary from fab to fab.

What do you mean by lambda for pnp and npn.
The foundry would usually give you npn or pnpnwith given emitter area as they modeled them for thoes area.

### e_fever_l

Points: 2
βnpn=99 , βpnp=49 , η=3.95,λ=1,Ege=1.143 V ,Vben=0.65V @ Ic=10 uA,Tn=300K
Vt=26mV @ 300K.
1---what is above circuit?
2---design above circuit such that IQ5=IQ6=100 uA ,Va=magic voltage@ T=Tn=300K, using equations calculate R2 & R1 for Va to be magic voltage.
3---calculate voltage Vout.
4---identify the startup circuit
5---design Rb such that Q4 turns off after start up.

thanks ,hr_rezaee and ambreesh,
this is a question in recruiting test . the circiut in attachment.
I guess η is γ,λ is α, in CMOS ANALOG CIRCUIT DESIGN ,second edition，P E.Allen ,(4.6-11),right??

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