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I IN. + -. A i I IN. +. +. -. -. + -. V O. I IN. R m I IN. Two port amplifier models based on the four different types of gain that include input and output impedance. I O. I O. Ro. + -. + -. Ri. V O. Ri. V O. V IN. Ro. A V V IN. I O. I O. Ro. + -. + -. V O.

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I O

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  1. IIN + - AiIIN + + - - + - VO IIN RmIIN Two port amplifier models based on the four different types of gain that include input and output impedance IO IO Ro + - + - Ri VO Ri VO VIN Ro AVVIN IO IO Ro + - + - VO VIN Ri Ri GmVIN Ro The models can be used to describe the same amplifier (Ro and Ri would be the same) Notice the Norton and Thevenin Equivalent Circuits

  2. Determining Two-port parameters THE RULES • Determine the DC operating point of the amplifier (The Q-point) • Set all independent voltage and current sources to zero* • Vsrc-> short • Isrc-> open • Replace all transistors with small signal models with parameters determined using the Q-point* • Configure circuit appropriately to determine the desired gain or impedance parameters (see next two slides) • * Steps 2 and 3 can be switched

  3. Determining Input and Output Impedances Input impedance Output impedance Vin = 0 implies shorting Vin Current and voltage reference conventions Iin Io Amplifier + Vo - + Vin -

  4. Current and Voltage reference conventions for determining Gain parameters Iin Io Amplifier + Vo - + Vin - Note Io is different

  5. IO IIN + - AiIIN Ri VO Ro + + - - Determining the 4 gain parameters IO Ro + - + - Ri VO VIN AVVIN Current Gain Voltage Gain IO IO Ro + - VIN + - + - VO Ri Ri VO IIN GmVIN RmIIN Ro Transconductance Transresitance Vo = 0 implies a short Io = 0 implies an open

  6. IO IIN + - AiIIN Ri VO Ro + + - - The gain parameters can be derived from one another IO IO Ro Ro + - + - Ri Ri VO VO IIN IIN RmIIN RmIIN Derivation Alternative Derivation

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