Basic components #001 - Operational Amplifier configurations

what's up my friends welcome back I'm starting a new video series with short videos that will provide basic knowledge about electronic components it is very important to know how each of the most common components work in order to be able to use them in our projects today we'll start with the first component of this video series the operational amplifier or better known as an op-amp we will take a look over the both common configurations of these amplifiers how to use them in different situations and finally we will take our breadboard and see some real tests for example here I have the LM 3 to 4 operational amplifier which basically are for op amps in just one IC it is not the best there is but will work just fine for our examples and see how they work so guys using this IC we'll take a look over the comparator configuration the voltage follower and why we need a voltage follower next we will see the non-inverting and inverting configuration and finally take a short look over the derivative and integral configuration of these op amps well guys let's prepare our breadboard and see some basic examples so let's get started [Music] this project is brought to you by jl CPCB which is a manufacturer of quick PCB prototypes for more than 10 years and is the site that i use for all my PCBs once design applied your Gerber files on the GLC PCB site get a full review of the PCB select your desired settings and order the PCB for amazing prices i've ordered ten of my prototype PCBs for only $2 and receive those in six days crazy right so order your quality PCB and make your projects look a lot more professional what's up my friends welcome back this has a configuration that we will study today first of all let's start with the most basic configuration of them all the comparator which is basically just the op-amp and nothing more but before that this is an operational amplifier IC the LM 3 to 4 this is its pin out and this is the basic op-amp symbol just a triangle with five pins those pins are called positive and negative input the output and the positive and negative supply of the amplifier in this entire tutorial we'll talk about the ideal amplifier but in real life all its aspect won't be perfect first ideal spec of the amplifier is that it's input impedance is practically infinite so no current could flow towards the amplifier on the input rails second spec is that the output impedance is low and current could flow inwards and outwards to the main supply third idea law and very important one is that the voltage on the positive and negative input will always be the same or at least the op-amp will try that even it won't succeed finally one more idea law the gain of an operational amplifier is very big or almost infinite but of course it won't amplify the input signal by infinite one obvious thing is that the output could have its maximum value the supply of the op amp it can be higher or lower than that so even with gain infinite the output will saturate at the input value great guys using the basic ID laws let's talk about the comparator configuration as its name tells us this configuration will compare which of the inputs is higher it works like this the output of this configuration is the difference between the two inputs multiplied by the amplifier gain since the gain is infinite whenever the positive input is lower than the negative will have a negative output and when the positive is higher than the negative a positive output now I place the LM 3 to 4 on the breadboard and supply positive and negative 12 volts to the supply pins now I connect ground to the negative input of the amplifier and the output to my oscilloscope at the positive input I will apply a sine wave with values from minus 2 to 2 volts the yellow line amongst low scope is the input and the green is the output as you can see when the input value is above ground the output is positive and when the input is below ground we have a negative output that's how this configuration works so when we should use this example well go and watch my tutorial on the Arduino base rpm meter it has an infrared sensor inside that gives a higher value each time it detects reflected light but the signal that gives is very low and oscillating a lot and the Arduino can't read that in order to pass that signal to digital values that the Arduino could read I've used this configuration and set the negative input to a value right below the peak so the voltage that the sensor gives and that resulted in a digital square wave that Marino could now read now let's see a limitation of this op-amp at the output I'll place a potentiometer so I could variety output load value when the low is high we have no problem but when I start lowering its value we can see that the output gets saturated that's because the op-amp has an output current limit right in this moment if we look at the output maximum voltage and then we measure the potentiometer value without changing its value we could obtain the current limit or maybe just check the datasheet of the amplifier well guys let's see the next example voltage follower this is the configuration for this example and as you can see we have now added this connection here that is called feedback the negative feedback one of the laws before was that the op-amp will try to make the voltage at the negative input equal to the one at the positive input by other ideal law we know that no current could flow toward the input rails so the only way to change the voltage at the negative pin here is towards the feedback now let's imagine we put five volts at the positive input the op-amp internally will do all it has to do in order to put exactly five volts at the output and at the same time to the negative input with the feedback so now we have the same value at the output as at the input that's why it's called a follower but you must wonder what stupid thing is this why apply five volts and obtain five volts as well well imagine this imagine that you have a circuit that works at let's say three volts I will draw that just as a black box for this example since we don't really care what circuit that is now let's say that you want to connect to that circuit and measure the voltage if you put a low impedance pro to it quilt will flow to that connected drill and by that we change the circuit value and we don't want that we don't want to measure the wrong values we want the real one so for that between the measured circuit and our connection we put a voltage follower in this way no current will flow towards the measuring device and by that we won't affect the measure circuit but we still have the real voltage at the output I've mounted this configuration on my breadboard and apply a sine wave to it as you can see the output is the same as the input and no current is flowing towards the op-amp okay guys let's take a look at the next configuration the inverting one since we have just looked at the voltage follower circuit instead of having just a simple connection between the output and the negative input let's add a resistor to that connection and another resistor at the negative input and connect the positive input to ground now let's apply real values so we could better understand how this works if the FIR resistor is 100 ohms and the second it's 10 and we apply one volt to the input this will happen a current will flow to r2 that current value is the input minus the voltage at the negative input point divided by r2 but the voltage at the negative point must be the same as the one at the positive input in this case ground we call this virtual ground since we don't really have a ground at that negative pin since no current could flow towards the op-amp the only route that the current could take is to the negative feedback rail this current value could also be expressed like the difference between the negative pin and the output divided by r1 since the negative input is ground all they're left with is that the negative output divided by r1 is the current value but this is the same value as sqrt 1 from this 2 equation we get that the gain which is expressed in the output divided by the input is negative r1 divided by r2 and there is our amplification r1 is 100 and r2 is 10 so the gain is minus 10 in this case so if we apply 1 volts at the input we get negative 10 at the output and vice versa that's why it is called inverted since the output is inverted to the input and just by changing the resistor values we can change the gain of the amplifier now I'm on this circuit on a breadboard with resistor values of 110 kilo ohms i supply positive and negative 12 volts to the amplifier and apply a 1 volts peak-to-peak sine wave at the input now on the oscilloscope the yellow line is the input and the green is the output as you can see the output is 10 times bigger and also inverted when the input is rising the output is falling and vice versa finally let's talk about the non inverting configuration this is it schematic now the positive pin is our main input of the circuit and the feedback is still connected at a negative input now as before the negative pin value is the same as the positive input in this case let's call it V in the coin that passes through r2 is vn- ground / r2 and the current through r1 is V out minus V in / r1 but we know once again that these two currents are equal so solving these two equation we get that the gain of this configuration is 1 plus R 1 / R to mount this example on the bread board using 110 kilo ohms resistor for r1 and r2 and supply power to the amplifier and once again apply a sine wave at the input of 1 volts peak-to-peak on the oscilloscope again the input with yellow and the output with green and we can see that the output is 11 times higher and that is not inverted so depending on what you want for your project just use one configuration or the other you could even connect two amplifiers in series and have double amplification or double inverted signal so the output won't be inverted well guys just as an extra I will show you the schematics for the differential and integral configuration as you can see now we have some capacitor as well with these configurations by applying a square wave at the input you could easily obtain a ramp also the derivative of a sine wave is a cosine wave as you can see here on my oscilloscope so there you go my friends now you know a bit more about basic op amps one interesting of digression it's a PD controller where we use the integrator differential inverter and summer configuration of the op amps and by changing the resistor and capacitor values we can tune the PD response well guys there you have it stay tuned for the next basic component tutorial where we'll take a look at another component have in mind that I explain only the ideal laws of the op amps in real life this won't be exact like this since each component will have its limitations such as no infinite input impedance output current limitation met common input amplification and so on please check the description of this video for all the configurations and more details on my webpage electronic comm also check my videos where I've used the op amps like the RPM meter and the a sequent probe to amplify a magnetic field sensor I even made a crew tree bit ABC using op amps so even this tutorial is very basic I hope that you learn something about op amps well guys I hope that you enjoyed this tutorial if so don't forget to click the I button like crazy and share this video with your friends if you have any question about this video or any other just leave it in the comment section below or my Q&A page also don't forget to subscribe and watch all my other way tutorials remember if you consider happy my projects check my patreon page as well thanks again and see you later guys [Music]

Channel: Electronoobs

Views: 56,041

Keywords: OpAmp, operational, amplifier, tutorial, basic, comparator, follower, voltage, inverted, non-inverted, integrator, differentiator, ramp, gain, circuit

Id: TLtZ-kTyGaQ

Length: 13min 1sec (781 seconds)

Published: Sun Apr 29 2018