EE5602_5_ARFaMT_AMP - RF/Microwave Transistor Types •...

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Unformatted text preview: RF/Microwave Transistor Types • Bipolar Junction Transistor – Ge-BJT, Si-BJT, SiGe-BJT – Heterojunction Bipolar Transistors (HBT) • Field Effect Transistor (FET) – Metal Insulator Semiconductor FET (MISFET) • Metal Oxide Semiconductor FET (MOSFET) – Junction FET (JFET) – MEtal Semiconductor FET (MESFET) – Hetero FET • High Electron Mobility Transistor (HEMT) – MOdulation Doped FET (MODFET) – pseudomorphic HEMT (pHEMT) Small Signal RF Transistor Models • Bipolar junction transistor: hybrid π • Field effect transistor c π B E E C c μ r π g v m π v π r o c gs G S S D c gd c ds r gs g v m π v i r ds Large Signal RF BJT Model C de C dc C jc C je B E C R BB R EE I R I F α F I F α R I R R CC Large Signal RF FET Model C GD C GS G S D r S V GD V GS I D r D Packaging Effects at RF/Microwave c π B E E C c μ r π g v m π v π r o r E r B r C L E L B L C Small Signal Amplifier Design • Transducer gain G T is a function of Γ L and Γ S . • Power gain G P is a function of Γ L . • Available gain G A is a function of Γ S . 2 22 2 2 21 2 2 1 1 1 1 L L S IN S T s s G Γ- Γ- × × Γ Γ- Γ- = 2 22 2 2 21 2 1 1 1 1 L L IN P s s G Γ- Γ- × × Γ- = 2 2 21 2 11 2 1 1 1 1 OUT S S A s s G Γ- × × Γ- Γ- = Stability • Unconditional stability: | Γ IN | < 1 and | Γ OUT | < 1, for all passive source and load impedances. • Conditional stability: | Γ IN | < 1 and | Γ OUT | < 1, for a certain range of source and load impedances. Also referred to as potentially unstable. Unconditional Stability For all Γ S and Γ L . Instability occur when the input or/and output port has a negative real part. This implies that | Γ IN | > 1 or | Γ OUT | > 1 and is frequency dependent. Define two types of stability, 1 1 1 1 11 21 12 22 ' 22 22 21 12 11 ' 11 F F S S OUT L L IN s s s s s s s s s s Γ- Γ + = = Γ Γ- Γ + = = Γ Stability Criteria • A passive source and load reflection coefficient has a maximum magnitude equal to 1, | Γ S | < 1 and | Γ L | < 1. • A magnitude of reflection coefficient for the input and output equal to 1 would be the boundary that separates stability from potential instability for a potentially unstable transistor. • Equating the magnitude of the input and output reflection coefficient to 1 will give the boundary for the load and source reflection coefficient that separates stability from potential instability. 1 1 1 1 11 21 12 22 22 21 12 11 = Γ- Γ + = Γ- Γ + S S L L s s s s and s s s s Stability Circles • Equating the magnitude of the input and output reflection coefficient to 1 results in circles in the load and source reflection coefficient planes. ( 29 ( 29 ( 29 ( 29 2 2 11 * * 22 11 2 2 11 21 12 2 2 11 21 12 2 2 11 * * 22 11 2 2 22 * * 11 22 2 2 22 21 12 2 2 22 21 12 2 2 22 * * 11 22 ∆- ∆- = ∆- = ⇒ ∆- = ∆- ∆-- Γ ∆- ∆- = ∆- = ⇒ ∆- = ∆- ∆-- Γ s s s C s s s R s s s s s s s s s C s s s R s s s s s s S S S L L L Test for Regions of Stability • The stable and unstable region can be found by using a...
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This note was uploaded on 01/11/2011 for the course EE 5602 taught by Professor Wingshingchan during the Spring '10 term at City University of Hong Kong.

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EE5602_5_ARFaMT_AMP - RF/Microwave Transistor Types •...

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