describe only that which relates with the regulation. A linear operational amplifier is a high gain with many applications in analog control systems. The figure shows two common types of capsules and the numbering of the pins, the symbol used in diagrams, forms of power and function that meets its output on pin 6.
operational A widely used is the 741 for its wide operating range, with a regular supply +15 volts and -15 volts (with two-way source .) If not using two-way power (Pin 4 connected to ground), the lowest voltage at pin 6 will not reach zero volts since the linearity is lost when approaching the limits of power on pins 4 and 7. An operational saving this problem is for example the CA3140E, responding either from zero volts when the same voltage is applied at pin 4.
As we shall see in the figure, the output of this interesting component is proportional to the difference of the input signals applied to pins 2 and 3 if and when it is not worth more than the supply voltage (positive or negative), after which time it was saturated. Depending on which of the inputs is greater, the output may be positive or negative with respect to the reference voltage or ground (for two-way power). The problem that arises in principle, is that the constant is about one hundred thousand, so a minimum difference between input signals produces the saturation of the operational, appearing at its output a voltage + V o-V (or zero volts if not two-way). The ability to detect small differences in the input signals has many applications, but not at all mentioned in regulation. This problem was easily saved if we do work in closed loop (feeding back the output to one input, which is normally pin 2 for reasons of its inner workings.)
The fact that the gain K is so high is actually a significant advantage when used with feedback. If the formula we set the K value by dividing the output voltage V6, the result will be almost zero, which shows that the operational always tend to equate the two input voltages and their difference is almost zero. Then we will see a few possibilities of operations.
If the operational tends to equalize the two inputs and the output is connected to one of them (a direct feedback as in the first case of the figure below), then the output will always tend to equalize Vs the entry Ve An operational feature of great practical value is that its input impedance is very high and its output is very low, so you can power a load (in vs out) without any change to the behavior of the voltage divider (ratio between the two resistors is equal to the ratio between the two strains on). Remember that when connecting multiple items and one of them is a burden for the former, their behavior varies and can not be studied separately, complicating their study. The purpose shown in the first case in the following figure is therefore to adapt the impedances for the purpose of circuit components or no charge to another. An operational with direct feedback is called a voltage follower.
In the second case of the previous figure we see its application as an inverting amplifier with adjustable gain if the resistance Rs is variable. Although you can connect two in series to provide a non-inverting amplifier, the same is achieved with a single operational (third case of the figure). It is imperative that the amplifier is an investor or investment but can not this be a factor also adjustable (first case in the following figure). As you might expect, these assemblies can play perfectly the role of a proportional controller. Gain formulas shown can be derived by considering the two voltages equal input. 
In the second case of the previous figure we see a montage to subtract two signals and applying a gain while the result (by itself includes a comparator and a proportional controller, with the command signal V2 and V1 the feedback). If you only want to use as a receiver is sufficient that R1 and R2 are equal. When necessary to make the sum signal, for example to add two or more actions of a regulator, we use a summing inverter (first case in the following figure) or a non-inverting adder (second case). In the latter case we see how they can join various signals and finally subtract the results. 
integral and derivative actions we can obtain as in the following figure. The resistor in parallel with the capacitor (first case) has no role in the signal obtained in the output but simply improving the internal functioning of the operational. The same consideration we do with the condenser of small capacity in the second case. 
The following example is a complete PID controller but very simplified, it would present some problems of adjustment parameters and would be more appropriate for a particular application with fixed parameters. However, if we consider the possibilities that have been described not find much difficulty in designing an adjustable regulator. 
complete this section showing a single power amplifier (second case in the previous figure) for the supply of small loads (small motors, lamps ...). As might be expected, an operational can not (usually) directly feeding a load. The control output is merely a signal that provides information and must be amplified in power (and voltage normally.)
Mario Dominguez Zambrano
EES
Section: 02
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