Semiconductors/Op-Amps

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Op-Amps Intro[edit]

Op-Amps stands for Operational Amplifier, a device usually manufactured as an Integrated Circuit (IC) . User don't need to know about the Itegrated Circuit inside in order to work with Op-Amps . All you need to know is that Op-Amps acts as an amplifier, it amplifies the difference of the 2 different voltages at input by a gain or amplification factor A

Output of an operational amplifier:

V_{O} = A(V^{+}-V^{-})

Ideally A is assumed to be equal to infinity. However, in practical op-amps, it has a high value. Furthermore, the gain A is a function of frequency.

Below is the most commonly used configuration of Op-Amps


Negative Amplifier[edit]

200
V_\mathrm{out} = - V_\mathrm{in} \frac{R_f}{R_\mathrm{in}}


  • The output voltage is a negative voltage equal to the input voltage amplified by a factor \frac{R_f}{R_\mathrm{in}}

Positive Amplifier[edit]

Opampnoninverting.svg
 V_\mathrm{out} = V_\mathrm{in} \left( 1 + {R_2 \over R_1} \right)
  • The output voltage is a positive voltage equal to the input voltage amplified by a factor  \left( 1 + {R_2 \over R_1} \right)

Positive Buffer[edit]

Opampfollowing.png  V_\mathrm{out} = V_\mathrm{in} \!\
  • From the circuit of Positive Amplifier, If R2 = 0 thì Vo = Vi

Negative Buffer[edit]

200
  • From the circuit of Negative Amplifier, If Rf/Ri = 1 then Vo = - Vi

Further reading[edit]