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1.6 Op-Amp Basics

1.6 Op-Amp Basics. Note: Terminals for dc supply are omitted. High input impedance Low output impedance Made using difference amplifiers having 2 inputs and at least 1 output. 1.6 Op-Amp Basics. Ideal. Practical. Input impedance, R i is typically very high

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1.6 Op-Amp Basics

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  1. 1.6 Op-Amp Basics Note: Terminals for dc supply are omitted High input impedance Low output impedance Made using difference amplifiers having 2 inputs and at least 1 output

  2. 1.6 Op-Amp Basics Ideal Practical • Input impedance, Ri is typically very high • Output voltage, Vo is amplifier gain times input signal taken through output impedance, Ro which is typically low. • Ideal op-amp would have infinite input impedance, zero output impedance and infinite voltage gain. AC equivalent circuit

  3. 1.6 Op-Amp Basics The input voltage V1 is applied to the inverting terminal through R1. The output voltage Vo is fed back to the inverting terminal through Rf. The non-inverting terminal is grounded The output voltage Vo is in antiphase with the input voltae Vi Basic Op-amp – constant-gain multiplier

  4. Basic Op-amp – constant-gain multiplier AC equivalent circuit 1.6 Op-Amp Basics Practical op-amp

  5. 1.6 Op-Amp Basics • Basic Op-amp – constant-gain multiplier • If the practical op-amp is replaced by an ideal op-amp, the equivalent circuit becomes;

  6. 1.6 Op-Amp Basics Basic Op-amp – constant-gain multiplier Redrawn equivalent circuit

  7. 1.6 Op-Amp Basics i) V1 only (set –AvVi = 0) ii) –AvVi only (set V1 = 0) Basic Op-amp – constant-gain multiplier By superposition theorem

  8. 1.6 Op-Amp Basics • Basic Op-amp – constant-gain multiplier Solving for Vi, gives us;

  9. 1.6 Op-Amp Basics • Basic Op-amp – constant-gain multiplier Usually and Then; The ratio Vo/V1 is dependent on the external components Rf and R1 only.

  10. 1.6 Op-Amp Basics • Basic Op-amp – unity gain If Rf= R1; Shown that the output voltage equal to input voltage with 180° phase inversion.

  11. 1.6 Op-Amp Basics • Basic Op-amp – constant magnitude gain If Rf = 10R1; Shown that the output voltage is equal to 10X the input voltage with 180° phase inversion.

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