Semiconductors/Op-Amps

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[edit] Op-Amps Intro

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:

VO = 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


[edit] Negative Amplifier

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}}

[edit] Positive Amplifier

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)

[edit] Positive Buffer

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


[edit] Negative Buffer

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

[edit] Further reading

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