Amplificadores operacionales

[pic 1][pic 2][pic 3][pic 4][pic 5]

MATERIAL

• 1 tablet PROTOBOARD experimentation.
• 3 coaxial cables with BNC-Cayman terminal.
• 4 Wire CAYMAN - Cayman.
• 3 Wire BANANA - Cayman.
• 2 LM741 (Operational Amplifier)
• 6 resistors 1k ¼ W.
• 3 10k Resistors 1 / 4W
• 5 100k resistors ¼ W.
• 1 560KΩ resistor ¼ W
• 1 Resistor 560Ω 1 ¼ W.
• 2 15KΩ resistors ¼ W
• 1 150KΩ resistor ¼ W
• 2 2.2KΩ resistors ¼ W
• 1 Resistor 3.3 KQ ¼ W
• 1 Resistor 2.2 KQ ¼ W
• 1 Resistor KQ 220 ¼ W
• 1 Resistor 4.7 Ohm at ¼ W
• 1 KQ resistor 15 ¼ W
• 1 KQ resistor 82 ¼ W
• 1 Capacitor 0.01 μ F
• 1 μ F capacitor 0.0022
• 1 100 pF capacitor

EQUIPMENT

• 1 power supply and dual + 12V - 12V
• 1 digital or analog multimeter.
• One Function Generator 10Hz-1MHz.
• 1 general purpose oscilloscope.

Objectives:

• Check analog circuits

• Inverting amplifier.
• Non-inverting amplifier.
• Voltage follower.
• Summing amplifier.
• Subtractor amplifier
• Integrator amplifier
• amplifier Shunt

• Interpret the results obtained for the above circuits.
• In all the operational amplifier circuits 741 to ± 12V supply is used.

INTRODUCTION

An operational amplifier (op-amp) is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output. In this configuration, an op-amp produces an output potential (relative to circuit ground) that is typically hundreds of thousands of times larger than the potential difference between its input terminals.

Operational amplifiers had their origins in analog computers, where they were used to do mathematical operations in many linear, non-linear and frequency-dependent circuits. Characteristics of a circuit using an op-amp are set by external components with little dependence on temperature changes or manufacturing variations in the op-amp itself, which makes op-amps popular building blocks for circuit design.

Op-amps are among the most widely used electronic devices today, being used in a vast array of consumer, industrial, and scientific devices. Many standard IC op-amps cost only a few cents in moderate production volume; however some integrated or hybrid operational amplifiers with special performance specifications may cost over $100 US in small quantities. Op-amps may be packaged as components, or used as elements of more complex integrated circuits.

The op-amp is one type of differential amplifier. Other types of differential amplifier include the fully differential amplifier (similar to the op-amp, but with two outputs), the instrumentation amplifier (usually built from three op-amps), the isolation amplifier (similar to the instrumentation amplifier, but with tolerance to common-mode voltages that would destroy an ordinary op-amp), and negative feedback amplifier (usually built from one or more op-amps and a resistive feedback network).

AMP INVESTOR

This show is so named because the output signal is input inverse in polarity, but could be higher, the same or lower, depending on the gain that we give to the amplifier in closed loop. The signal as shown in the figure, is applied to the inverter or negative terminal of the amplifier and the positive or non-inverting takes mass. Resistor R2, which runs from the outlet to the negative input terminal is called feedback.

VOLTAGE FOLLOWER

The voltage follower with an ideal op amp, gives just Vout = Vin

But this result is a very useful application , because the input impedance of the op amp is very high , providing an insulating effect with respect to the output of the input signal , negating the effects of "burden" . This makes it a useful first stage circuit.

The voltage follower is often used in logic circuits, to build buffers.

SUMMING AMPLIFIER INVESTOR

The adder is a useful circuit, based on the standard configuration of the inverting operational amplifier. This circuit combines multiple inputs, ie, can add algebraically two (or more) signals or voltages to form the sum of these signals.

The reason to use an operational amplifier to add multiple input signals, is to prevent the interaction between them, so that any change in the voltage of the entries will not affect other inputs.

SUBTRACTING AMPLIFIER

Some applications require that the "difference" between two voltages is amplified. This is the case of a control system in which the comparator tom to the difference between the input voltage and the feedback voltage. Another example is found in biomedical applications, in which a measurement of the voltage difference between two points of the patient's body is performed. In these cases the differential op-amp configuration shown in Figure (5) is required. If it is grounded V1, V2 then contemplates an inverting configuration. If V1 is grounded (through a voltage divider), you will see a non-inverting configuration.

INTEGRATING AMPLIFIER

The integrating circuit is a circuit with an operational amplifier that performs the mathematical operation of integration. The circuit acts as a storage element which produces a voltage output that is proportional to the time integral of the input voltage.

If an input signal constantly changing the input of an integrator amplifier is applied, for example a square wave, the capacitor is charged and discharged in response to changes in the input signal. Thus, an output signal in sawtooth shape, whose frequency depends on the RC time constant of the combination of resistor and capacitor is created.

The output of this circuit can be predicted by the following equation:

[pic 6]

SHUNT AMPLIFIER

Shunt circuit performs the mathematical derivation operation, so that the output of this circuit is proportional to the time derivative of the input signal. In other words, the output is proportional to the rate of change of the input signal.

The magnitude of the output is determined by the rate at which the voltage changes the entry applies. The faster the changes in the input, the higher the output voltage.

The shunt circuit is exactly the opposite of the integrator circuit. As with the integrator circuit, the shunt circuit is a resistor and a capacitor forming a RC network through the operational amplifier, but in this case, reactance, XC, is connected to the inverting input of the operational amplifier, while resistance, RF, form negative feedback element. The reactance of the capacitor plays an important role in the performance of a shunt circuit.

In short, the necessary components to be connected to an operational amplifier are:

A capacitor connected to the inverting input.

A feedback resistor connected between the output and the inverting input.

DEVELOPMENT

INVERTING AMPLIFIER

We build the circuit of the image.[pic 7]

With  a  sinusoidal  signal  of  1  Vppand  a  frequency  of  1  kHz  in  the  input  voltage,  we  get  the following waves in the oscilloscope(Image 2),wherethe channel 1 corresponds to input voltage, and  channel  2  corresponds  to  output  voltage.Notice  that  the  voltage  of  channel  2  is  inverse respectto channel 1.

V/div channel 1: 200mV                

V/div channel 2: 2 V

Sec/div:250μS

[pic 8]

NON-INVERTING AMPLIFIER

[pic 9]

With   a   sinusoidal   signal   of   1   Vpp   and   a frequency  of  1  kHz  in  the  input  voltage,  we build the circuit showed in the image.

When   we   connect   the   input and   output voltages   to   the  oscilloscope,   we   get   the following  waves,  the  channel  1  corresponds to  input  voltage,  and  channel  2  corresponds to output voltage.

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