Basic Op Amp circuits: Difference between revisions

Revision as of 15:41, 11 January 2010

Buffer Amplifier

Used to transfer voltage but not current to the following circuit. This amplifier can be used to negate the loading effects. No current flows through the amplifier, thus there is no voltage drop through the input resistor (going to the buffer amplifier).

Inverting Amplifier

Uses negative feedback to invert and amplify voltage. Using nodal analysis at the negative terminal, the gain is found to be $- \frac{R_{2}}{R_{1}}$

Summing Amplifier

$V_{o} = - R_{f} (\frac{V_{3}}{R_{3}} + \frac{V_{2}}{R_{2}} + \frac{V_{1}}{R_{1}})$
If all resistances are equal, then the output voltage is the (negative) sum of the input voltages

Noninverting Amplifier

Differential Amplifier

$V_{o} = V_{2} \frac{(R_{1} + R_{f}) R_{g}}{(R_{2} + R_{g}) R_{1}} - V_{1} \frac{R_{f}}{R_{1}}$
If you let $R_{1} = R_{2}$ and $R_{g} = R_{f}$ then the equation simplifies to $V_{o} = \frac{R_{f}}{R_{1}} (V_{2} - V_{1})$

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 [[Image:InvertingAmplifier.png|thumb|300px|Inverting Amplifier]]
 *Uses negative feedback to invert and amplify voltage. Using nodal analysis at the negative terminal, the gain is found to be <math>-\frac{R_2}{R_1}</math>
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 ==Summing Amplifier==
 [[Image:Summing_Amplifier.PNG‎|thumb|300px|Summing Amplifier]]
 *<math>V_o=-R_f \left( \frac{V_3}{R_3}+\frac{V_2}{R_2}+\frac{V_1}{R_1}\right)</math>
 *If all resistances are equal, then the output voltage is the (negative) sum of the input voltages
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 ==Noninverting Amplifier==
 [[Image:Noninverting_Amplifier.PNG‎|thumb|300px|Noninverting Amplifier]]
 *<math>V_o=V_{in} \left(1+\frac{R_2}{R_1}\right)</math>
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 ==Differential Amplifier==
 [[Image:Differential_Amplifier_2.PNG‎|thumb|300px|Differential Amplifier ]]
 *<math>V_o=V_2\frac{(R_1+R_f)R_g}{(R_2+R_g)R_1}-V_1\frac{R_f}{R_1}</math>
 *If you let <math>R_1=R_2\,</math> and <math>R_g=R_f\,</math> then the equation simplifies to <math>V_o=\frac{R_f}{R_1}(V_2-V_1)</math>