Equivalent Circuit Model

Monday, 10 September 2018

12:14 PM

Machine generated alternative text: Equivalent circuit model • An Op Amp is modelled from its input terminals by an input resistor Ri, and from its output terminal by a voltage- controlled voltage source in series o with an output resistor Ro. • The output voltage vo is given by: vo = Ava = A(V2 — VI) Typical range for Op Amp parameters Avd Parameter Open-loop gain, A Input resistance Ri Output resistance Ro Supply voltage, Vcc Typical range 105 to 108 105 to 1013 Q 10 to 100 Q 5 to 24 V Ideal value 00 0 • A: Open-loop voltage gain vct: Differential input voltage • VI : Inverting terminal voltage to the ground • 1.12: Non-inverting terminal voltage to the ground • • Ro: Thevenin equivalent resistance seen at the output terminals • Ri: Thevenin equivalent resistance seen at the input terminals

Equivalent Circuit Model

Op Amps can be modelled with an input resistor R_i, and the output as a voltage-controlled voltage source with an output resistor

 

V_o = Av_d = A(v_2 - v_1)

 

R_o - thevenin equivalent resistor from output terminals

R_i - thevenin equivalent resistor from input terminals

 

 

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