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[http://tinyurl.com/yxrdh8gx opamp as a comparator] | [http://tinyurl.com/yxrdh8gx opamp as a comparator] | ||
* the opamp's output can also directly follow one of its input voltages, but providing more current. This is the basis building block of opamp based | * the opamp's output can also directly follow one of its input voltages, but providing more current. This is the basis building block of opamp based amplifiers and is called "voltage follower" or "buffer". | ||
[http://www.falstad.com/circuit/circuitjs.html?cct=$+1+0.000005+10.20027730826997+50+5+43%0Ag+-384+-48+-384+-32+0%0Av+-384+-48+-384+-128+0+1+100+5+0+0+0.5%0Ag+-272+-48+-272+-32+0%0Ax+-496+-235+-330+-232+4+18+The%5CsSource%5CsFollower%0Ax+-506+33+181+36+4+12+Once%5Csyou%5Csapply%5Csa%5Csfeedback%5Cspath%5Csfrom%5Csthe%5Csopamp's%5Csoutput%5Csto%5Csthe%5Csnegative%5Csinput,%5Csthe%5Csoutput%5Csvoltage%5Csdirectly%5Csfollws%5Csthe%5Csinput%5Csvoltage.%0Ax+-506+57+-440+60+4+12+Why%5Csis%5Csthat?%0Ax+-506+82+-3+85+4+12+When%5Csthe%5Cssinwave%5Csof%5Csthe%5Cspositive%5Csinput%5Csgoes%5Csup,%5Csthe%5Csoutput%5Cswill%5Csalso%5Csgo%5Csup%5Cs(with%5Csvery%5Cshigh%5Csgain).%0Ax+-509+109+299+112+4+12+%5CsBut%5Cssince%5Csthis%5Cshigh%5Csgain%5Cssignal%5Csis%5Csreflected%5Csback%5Csto%5Csthe%5Csnegative%5Csinput%5Csit%5Cswill%5Cscounteract%5Cson%5Csthe%5Csoutput,%5Csforcing%5Csthe%5Csoutput%5Cseven%5Csmore%5Csto%5Csthe%5Csminus%5Csdirection.%5Cs%0Aa+-384+-144+-272+-144+8+15+-15+1000000+2.8621324318134485+2.8621610531377666+100000%0Ap+-272+-144+-272+-48+1+0%0Aw+-272+-144+-240+-144+0%0A207+-240+-144+-192+-144+0+output%0A207+-384+-128+-416+-128+0+input%0Aw+-272+-144+-272+-208+0%0Aw+-272+-208+-384+-208+0%0Aw+-384+-208+-384+-160+0%0Ax+-508+134+367+137+4+12+However,%5Csfeedback%5Csis%5Csan%5Csendless%5Csprocess%5Csand%5Csas%5Cssuch%5Csthe%5Csforce%5Csto%5Csthe%5Csminus%5Csdirection%5Cswill%5Csbe%5Csreflected%5Csback%5Csto%5Csthe%5Csinput%5Csagain,%5Csforcing%5Csthe%5Csoutput%5Csto%5Csbe%5Cspositive%5Csagain.%0Ax+-510+164+175+167+4+12+All%5Csthose%5Cspositive%5Csand%5Csnegative%5Csforces%5Cswill%5Csmagically%5Cssum%5Csup%5Csin%5Csevery%5Csmoment%5Csin%5Cstime,%5Csforcing%5Csthe%5Csoutput%5Csto%5Csexactly%5Csfollow%5Csthe%5Csinput!%0Ax+-510+195+87+198+4+12+This%5Cscircuit%5Csis%5Csalso%5Cscalled%5Csa%5Cs%22buffer%22%5Cssince%5Csit%5Cscan%5Csbe%5Csused%5Csto%5Csrepeat%5Csa%5Csweak%5Cssignal.%5CsMeaning%5Csamplifiying%5Csthe%5Cscurrent,%5Cs%0Ax+-511+222+-63+225+4+12+since%5Csthe%5Csopamp%5Cscan%5Csprovide%5Csmore%5Cscurrent%5Csat%5Csthe%5Csouput%5Csthen%5Csis%5Csavailable%5Csat%5Csits%5Csinputs.%0Ao+9+64+0+4098+20+0.1+0+3+1+0+1+3%0A stabilized opamp as a source follower] | [http://www.falstad.com/circuit/circuitjs.html?cct=$+1+0.000005+10.20027730826997+50+5+43%0Ag+-384+-48+-384+-32+0%0Av+-384+-48+-384+-128+0+1+100+5+0+0+0.5%0Ag+-272+-48+-272+-32+0%0Ax+-496+-235+-330+-232+4+18+The%5CsSource%5CsFollower%0Ax+-506+33+181+36+4+12+Once%5Csyou%5Csapply%5Csa%5Csfeedback%5Cspath%5Csfrom%5Csthe%5Csopamp's%5Csoutput%5Csto%5Csthe%5Csnegative%5Csinput,%5Csthe%5Csoutput%5Csvoltage%5Csdirectly%5Csfollws%5Csthe%5Csinput%5Csvoltage.%0Ax+-506+57+-440+60+4+12+Why%5Csis%5Csthat?%0Ax+-506+82+-3+85+4+12+When%5Csthe%5Cssinwave%5Csof%5Csthe%5Cspositive%5Csinput%5Csgoes%5Csup,%5Csthe%5Csoutput%5Cswill%5Csalso%5Csgo%5Csup%5Cs(with%5Csvery%5Cshigh%5Csgain).%0Ax+-509+109+299+112+4+12+%5CsBut%5Cssince%5Csthis%5Cshigh%5Csgain%5Cssignal%5Csis%5Csreflected%5Csback%5Csto%5Csthe%5Csnegative%5Csinput%5Csit%5Cswill%5Cscounteract%5Cson%5Csthe%5Csoutput,%5Csforcing%5Csthe%5Csoutput%5Cseven%5Csmore%5Csto%5Csthe%5Csminus%5Csdirection.%5Cs%0Aa+-384+-144+-272+-144+8+15+-15+1000000+2.8621324318134485+2.8621610531377666+100000%0Ap+-272+-144+-272+-48+1+0%0Aw+-272+-144+-240+-144+0%0A207+-240+-144+-192+-144+0+output%0A207+-384+-128+-416+-128+0+input%0Aw+-272+-144+-272+-208+0%0Aw+-272+-208+-384+-208+0%0Aw+-384+-208+-384+-160+0%0Ax+-508+134+367+137+4+12+However,%5Csfeedback%5Csis%5Csan%5Csendless%5Csprocess%5Csand%5Csas%5Cssuch%5Csthe%5Csforce%5Csto%5Csthe%5Csminus%5Csdirection%5Cswill%5Csbe%5Csreflected%5Csback%5Csto%5Csthe%5Csinput%5Csagain,%5Csforcing%5Csthe%5Csoutput%5Csto%5Csbe%5Cspositive%5Csagain.%0Ax+-510+164+175+167+4+12+All%5Csthose%5Cspositive%5Csand%5Csnegative%5Csforces%5Cswill%5Csmagically%5Cssum%5Csup%5Csin%5Csevery%5Csmoment%5Csin%5Cstime,%5Csforcing%5Csthe%5Csoutput%5Csto%5Csexactly%5Csfollow%5Csthe%5Csinput!%0Ax+-510+195+87+198+4+12+This%5Cscircuit%5Csis%5Csalso%5Cscalled%5Csa%5Cs%22buffer%22%5Cssince%5Csit%5Cscan%5Csbe%5Csused%5Csto%5Csrepeat%5Csa%5Csweak%5Cssignal.%5CsMeaning%5Csamplifiying%5Csthe%5Cscurrent,%5Cs%0Ax+-511+222+-63+225+4+12+since%5Csthe%5Csopamp%5Cscan%5Csprovide%5Csmore%5Cscurrent%5Csat%5Csthe%5Csouput%5Csthen%5Csis%5Csavailable%5Csat%5Csits%5Csinputs.%0Ao+9+64+0+4098+20+0.1+0+3+1+0+1+3%0A stabilized opamp as a source follower] | ||
* once you provide a voltage divider circuit in the feedback loop of an voltage follower, you are able to control the gain of the output port. This means the voltage of the output can be a scaled version of the input, either attenuating or amplifying the input voltage. Depending on whether the voltage divider is applied on the positive or negative input, the output is an inverted or non-inverted version of the input voltage. The two basic building blocks are shown below. | |||
[http://www.falstad.com/circuit/circuitjs.html?cct=$+1+0.000005+10.20027730826997+50+5+43%0Ag+-304+16+-304+32+0%0Av+-448+16+-448+-64+0+1+100+1+0+0+0.5%0Ax+-411+-158+-231+-155+4+18+The%5CsInverting%5CsAmplifier%0Aa+-304+0+-192+0+8+15+-15+1000000+0.00009213554917863564+0+100000%0Aw+-192+0+-160+0+0%0A207+-160+0+-112+0+0+output%0Aw+-192+0+-192+-64+0%0Aw+-304+-64+-304+-16+0%0Ar+-288+-64+-208+-64+0+10000%0Aw+-288+-64+-304+-64+0%0Aw+-208+-64+-192+-64+0%0Ar+-448+-64+-304+-64+0+1000%0Ag+-448+16+-448+32+0%0Ax+-365+72+-208+75+4+12+Gain%5Cs%5Cq%5CsR2%5Cs/%5CsR1%5Cs%5Cq%5Cs10k/1K%5Cs%5Cq%5Cs10%0Ao+1+64+0+4098+5+0.1+0+2+1+3%0Ao+5+64+0+4099+10+0.00009765625+1+2+5+3%0A Inverting Opamp] | [http://www.falstad.com/circuit/circuitjs.html?cct=$+1+0.000005+10.20027730826997+50+5+43%0Ag+-304+16+-304+32+0%0Av+-448+16+-448+-64+0+1+100+1+0+0+0.5%0Ax+-411+-158+-231+-155+4+18+The%5CsInverting%5CsAmplifier%0Aa+-304+0+-192+0+8+15+-15+1000000+0.00009213554917863564+0+100000%0Aw+-192+0+-160+0+0%0A207+-160+0+-112+0+0+output%0Aw+-192+0+-192+-64+0%0Aw+-304+-64+-304+-16+0%0Ar+-288+-64+-208+-64+0+10000%0Aw+-288+-64+-304+-64+0%0Aw+-208+-64+-192+-64+0%0Ar+-448+-64+-304+-64+0+1000%0Ag+-448+16+-448+32+0%0Ax+-365+72+-208+75+4+12+Gain%5Cs%5Cq%5CsR2%5Cs/%5CsR1%5Cs%5Cq%5Cs10k/1K%5Cs%5Cq%5Cs10%0Ao+1+64+0+4098+5+0.1+0+2+1+3%0Ao+5+64+0+4099+10+0.00009765625+1+2+5+3%0A Inverting Opamp] | ||
[http://www.falstad.com/circuit/circuitjs.html?cct=$+1+0.000005+10.20027730826997+50+5+43%0Ag+-448+112+-448+128+0%0Av+-448+112+-448+32+0+1+100+1+0+0+0.5%0Ax+-411+-158+-192+-155+4+18+The%5CsNon-Inverting%5CsAmplifier%0Aa+-304+0+-192+0+8+15+-15+1000000+0.1842741783321202+0.18429444849173673+100000%0Aw+-192+0+-160+0+0%0A207+-160+0+-112+0+0+output%0Aw+-192+0+-192+-64+0%0Aw+-304+-64+-304+-16+0%0Aw+-448+32+-448+16+0%0Ar+-288+-64+-208+-64+0+10000%0Aw+-288+-64+-304+-64+0%0Aw+-208+-64+-192+-64+0%0Ar+-448+-64+-304+-64+0+1000%0Aw+-448+16+-304+16+0%0Ag+-448+-64+-448+-32+0%0Ax+-365+72+-168+75+4+12+Gain%5Cs%5Cq%5Cs1%5Cs%5Cp%5CsR2%5Cs/%5CsR1%5Cs%5Cq%5Cs1%5Cs%5Cp%5Cs10k/1K%5Cs%5Cq%5Cs11%0Ao+1+64+0+4098+5+0.1+0+2+1+3%0Ao+5+64+0+4099+20+0.00009765625+1+2+5+3%0A Non-Inverting Opamp] | [http://www.falstad.com/circuit/circuitjs.html?cct=$+1+0.000005+10.20027730826997+50+5+43%0Ag+-448+112+-448+128+0%0Av+-448+112+-448+32+0+1+100+1+0+0+0.5%0Ax+-411+-158+-192+-155+4+18+The%5CsNon-Inverting%5CsAmplifier%0Aa+-304+0+-192+0+8+15+-15+1000000+0.1842741783321202+0.18429444849173673+100000%0Aw+-192+0+-160+0+0%0A207+-160+0+-112+0+0+output%0Aw+-192+0+-192+-64+0%0Aw+-304+-64+-304+-16+0%0Aw+-448+32+-448+16+0%0Ar+-288+-64+-208+-64+0+10000%0Aw+-288+-64+-304+-64+0%0Aw+-208+-64+-192+-64+0%0Ar+-448+-64+-304+-64+0+1000%0Aw+-448+16+-304+16+0%0Ag+-448+-64+-448+-32+0%0Ax+-365+72+-168+75+4+12+Gain%5Cs%5Cq%5Cs1%5Cs%5Cp%5CsR2%5Cs/%5CsR1%5Cs%5Cq%5Cs1%5Cs%5Cp%5Cs10k/1K%5Cs%5Cq%5Cs11%0Ao+1+64+0+4098+5+0.1+0+2+1+3%0Ao+5+64+0+4099+20+0.00009765625+1+2+5+3%0A Non-Inverting Opamp] | ||