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Explanation of 1/3 rule and 1/10 rule in BJT

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mannnish

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hi
i am looking for concepts on 1/3 rule and 1/10 rule in bjt...
please post your concepts on these rules.......

i would be very thankful....
 

Re: a question on bjt

I've been studying Electronics but I dont know what ur talking about. Sorry but what are these rules and what do u want to know about them?
 

a question on bjt

It may be a general concept and not specific for electronic design.
please specify it exactly.

Added after 2 minutes:

in this article you can find 1/3 rule:

Theoretical study of the electronic properties of narrow single-walled carbon nanotubes: Beyond the local density approximation.
The Journal of Chemical Physics -- December 1, 2004 -- Volume 121, Issue 21, pp. 10376-10379

Added after 30 seconds:

Don't forget Help buttom
 

Re: a question on bjt

i thing it is related with the size of bjt or in concern about layout.
 

Re: a question on bjt

FROM MY POINT OF THE 1/3rd AND 1/10th RULES ARE THERE IN MATHEMATICS AND ALSO THERE IS SIMPSON"S 1/3 RD AND 3/8TH RULE WHICH IS GENERALLY USED IN THE CALCULATION OF ANITEGRAL NUMERICALLY

Added after 42 seconds:

FROM MY POINT OF THE 1/3rd AND 1/10th RULES ARE THERE IN MATHEMATICS AND ALSO THERE IS SIMPSON"S 1/3 RD AND 3/8TH RULE WHICH IS GENERALLY USED IN THE CALCULATION OF ANITEGRAL NUMERICALLY
 

Re: a question on bjt

Hi
1/3 and 1/10 rules r emperical and not of technical standard designs,whch iu believe.
 

Re: a question on bjt

these r designing rules
u can learn these through "microelectronic circuits by sedra and simith 4th editon" see chapter number 4 in which four tecniques of biasing tranistor
u see it in first technique of biasing
 

Re: a question on bjt

I think you're talking about the rules for biasing a 4-resistor common emitter amplifier. The "1/3 rule" is to let one third of the supply voltage over the emitter resistor, and 1/3 over the collector-emitter junction and 1/3 over the collector resistor. Doing so inserts feedback through the emitter resistor: A change in the base-emitter voltage (mainly because of temperature changes) will be swamped by the larger voltage over the emitter resistor.
The 1/10 rule is to let the base current be 1/10 of the current through the two base resistors. A change in the current from the supply will only result in a small change in base current and so keeps the transistor stable.
Using these rules you insert feedback to the amplifier and it also makes the resistor values less critical. More theory on this is found in litterature on analog electronics, see Sedra for example.

These are only rules of thumb and not optimal. To find the optimal operating point you can write the KCL-KVL equations and solve the extreme value problem with some constraints. A simpler way is to use some simulator (Spice).
 

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