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I'm studying about the AC equivalent model of BJT and in the re model, it said that:

"As the base current increases the slope of the line increases, resulting in an increase in output impedance with increase in base and collector current"

Characteristic curve

I thought that the impedance is equal to the ro in the denominator, so base on the formula of the slope in the picture then if the slope increases, the value of ro decreases and therefore the impedance should decrease rather than increase.

Am I missing something?

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  • \$\begingroup\$ The "steeper" the slope is the lower the ro resistance is. i.sstatic.net/gV6wP.png \$\endgroup\$
    – G36
    Commented Mar 28, 2020 at 17:12
  • \$\begingroup\$ Where did you read such surprising "explanations"? I suppose - any obscure internet source? \$\endgroup\$
    – LvW
    Commented Mar 28, 2020 at 17:36
  • \$\begingroup\$ Electronic Devices and Circuit Theory (11th Edition) by Robert L. Boylestad, Louis Nashelsky - page 259. That's why I felt so confused because it's in a textbook. \$\endgroup\$
    – Trung
    Commented Mar 28, 2020 at 17:39

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"As the base current increases the slope of the line increases, resulting in an increase in output impedance with increase in base and collector current"

They got it wrong - as the slope increases you get more amps per volt so conductance increases and conductance is the inverse of resistance.

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    \$\begingroup\$ Yes....the quoted text is without sense...: "As the base current increases......resulting in an increase in.....base ...current." Crazy! \$\endgroup\$
    – LvW
    Commented Mar 28, 2020 at 17:34

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