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NPN - linear or saturation region region for GPIO switching

Discussion in 'Electronic Design' started by [email protected], Jun 26, 2013.

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  1. Guest

    I am using a general purpose BC846 NPN transistor collector to pull an IC'sEnable pin down. The base of BC846 is driven a source that can only source0.2mA of current. Since I only need to turn ON the transistor to pull the Enable pin down, base drive of 0.2mA is sufficient. Is 0.2mA of base current sufficient to fully turn ON the transistor or it will operate in the linear region? What will be the power dissipation if the transistor is operatedin linear region compared to saturation? The system may be in this state for several weeks. Are there any potential issues if the transistor is operated in this way.

    thanks
    srcherukuri
     
  2. Guest

    What textbook are you using? Anyone who would think enough about those various issues would not be so ignorant of the answer.
     
  3. Guest

    Thanks. BC846 must sink about 50uA.
     
  4. Guest

    Thanks for the response. Pull up is 330K to 16V.
     
  5. Guest

    The collector current is always limited by few tens of uA due to high valuepull up resistor and the IC pin internal limitation. Base drive is max 0.2mA. With this limitation of base current and collector current will the transistor ever reach saturation? If it doesn't, will operating it in leaner mode continuously for long periods cause any issues due to high Vce?
     
  6. josephkk

    josephkk Guest

    You are extremely unlikely to need any more base drive than collector
    current. You could probably cut it the 1/10 of required collector
    current.

    ?-)
     
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