View source for Analog Circuits and Interfaces/introduction to electronics

Here you find learning material in the form of circuit simulations, that lead you to the understanding of amplifiers and other signal conditioning circuits that we use throughout the course. Feel free to experiment with them, they are editable and saved via the encoded URL. You cannot destroy them and it is easy to share edited versions. [http://bait-consulting.com/publications/circuit_simulator_manual.pdf Here] is an introduction to the circuit simulator.

* The foundation of understanding electric circuits is Ohm's law.
[http://tinyurl.com/y579oadd Ohm's Law]
* A very powerful concept is the voltage divider, it allows us to attenuate (but not amplify!) any voltage in any circuit
[http://tinyurl.com/yxhsk8sc voltage divider with even resistors]
* We will use the OpAmp (=operational amplifier) to amplify the small signals from our microphones to usable and less noisy signals before we digitize them in the computer. The opamp (= operational amplifier) is a three port device and its circuit diagram is a triangle. It has a positive and a negative input terminal and an output terminal. The most basic opamp circuit is the "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 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]

* 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+-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]