Semiconductors/Op-Amps

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:

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

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

Inverting amplifier

$V_{\mathrm {out} }=-V_{\mathrm {in} }{\frac {R_{f}}{R_{\mathrm {in} }}}$

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

Positive Amplifier

Positive amplifer.

$V_{\mathrm {out} }=V_{\mathrm {in} }\left(1+{R_{2} \over R_{1}}\right)$

• 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

$V_{\mathrm {out} }=V_{\mathrm {in} }\!\$

• From the circuit of Positive Amplifier, If R₂ = 0 thì V_o = V_i

Negative Buffer

Inverting amplifier

• From the circuit of Negative Amplifier, If R_f/R_i = 1 then V_o = - V_i

Further reading

• Electronics/Op-Amps