16.HBTs_ft - HBT Parasitics HBT Parasitics 1 CEB and RB2...

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1 HBT HBT Parasitics Parasitics •C EB and R B2 need explanation
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2 HBTs HBTs : : f f T Sections 10.1, 10.4, Chapter 11 of course text: 1. HBT capacitance 2. Derivation of f T 3. Improving f T in HBTs 4. f max 5. BiCMOS
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3 Capacitance Capacitance Generally: V + + - - V Q C 1 Specifically: 2
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4 Emitter Emitter - - base junction base junction - - storage capacitance storage capacitance E B C QNE QNC QNB V BE + BE j E j EB V Q C = , , Q E,j is the change in charge entering the device through the emitter and creating the new width of the depletion layer (narrowing it in this example), • in response to a change in V BE (with E & C at AC ground). • It can be regarded as a parallel-plate cap. B j EB W A C ε , W B2 W B1 What is the voltage dependence of this cap?
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5 Emitter Emitter - - base base base base - - storage capacitance: concept storage capacitance: concept E B C QNE QNC QNB V BE + BE b E b EB V Q C = , , Q E,b is the change in charge entering the device
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This note was uploaded on 11/10/2010 for the course EECE 480 taught by Professor David during the Fall '09 term at The University of British Columbia.

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16.HBTs_ft - HBT Parasitics HBT Parasitics 1 CEB and RB2...

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