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BJT

Wikipedia - Slope

BJT small signal model
  1. gm = d(IC)/d(VBE) = d/dVBE * ICS * exp(VBE/VT) = IC/VT
  2. rO = [d(IC)/d(VBE)]-1 = [d/dVCE * ICS * exp(VBE/VT)(1 + VCE/VA)]-1 ~ VA/IC
  3. rBE = [d(IB)/d(VBE)]-1 = (1/beta_f * d(IC)/d(VBE)]-1 ~ beta_f/gm
  4. beta_f = IC/IB
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