741 Op-Amp Circuit Section 8.1 (Razavi). Equivalent Circuit of an Op-Amp Characteristics: Negligible input current Large input AC resistance Small AC.

741 Op-Amp Circuit

Section 8.1 (Razavi)

Equivalent Circuit of an Op-Amp

Characteristics: Negligible input currentLarge input AC resistanceSmall AC output resistanceLarge Voltage Gain

Op-Amp as an Amplifier

(non-inverting input)

(inverting input)

Op-Amp is a circuit that amplifies the differencebetween the inputs.

ST UA741CN Op-Amp

ST UA741 CN Schematic

Spec Sheet for ST UA741 CN

UA741 CN Specs (Cont.)

Topics

• Non-Inverting Amplifier• Inverting Amplifier• Integrator• Differentiator

Non-Inverting Amplifier (Ideal)

(Assumption: Ao is infinite)

Inverting Amplifier

Input impedance: R2

Trade off: Input impedance versus voltage gain.

Virtual Ground Versus An Ordinary Ground

Node X is a virtual ground, but not an ordinary ground.

If X were an ordinary ground, current from Vin would bediverted from R1since R1 represents a path of high impedance.

Differential Amplifier

If R1=R2 and Rf=Rg, then Vout/(V2-V1)=(Rf/R1)

Instrumentation Amplifier