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Interpretation of Results:

We familiarized ourselves in different types of op amps and its packaging. Thereare 4 different types of packaging for an op amp. These are TO-5 Metal “Can” (8-pin),Flat-pack (10-pin), DIP (14-pin) and MINI-DIP (8-pin). We are given a schematic

diagram and its actual image and we just labeled the pins of op amps and studied thefunctions of every pin. The op amp given to us was an LF441 with 8 pins mini dual-in-line package. The schematic symbol of an LF441 has 8 pins. Pin 1 and pin 5 are offsetnull, pin 2 is for inverting input and pin 3 is for non-inverting input, pin 6 is the output, pin7 is for positive supply terminal and pin 4 is for the negative supply terminal and pin 8 isnot connected. Typical op amps use several types of signal functions. Positive andnegative supply terminals connect to the system power supply rails and provideoperating power. Null, or nulling, terminals connect to an external voltage and allow for op amp offset voltage adjustment. Inverting (-)and noninverting (+) terminals connect tothe circuit input voltages. An output terminal drives the external circuit load.

There are three basic circuit configurations for operational amplifier: open-loopmode, inverting amplifier and non-inverting amplifier. Open-loop mode refers to theabsence of a feedback loop from the output to the input, inverting amplifier inverts andscales the input signal and non-inverting amplifier makes the positive input remains apositive output.

 An attenuator is an electronic device that reduces the amplitude or power of asignal without appreciably distorting its waveform. An attenuator is effectively theopposite of an amplifier, though the two work by different methods. While an amplifier provides gain, an attenuator provides loss, or gain less than 1. Attenuators are usuallypassive devices made from simple voltage divider networks. Switching between

different resistances forms adjustable stepped attenuators and continuously adjustableones using potentiometers.

We used the attenuator circuit block and used the function generator to have a10V peak to peak at a frequency of 10Hz. Using an oscilloscope, we determined theoutput voltage. Vo = 940mV and then we computed for the Av = Vo/Vi. We got Av =0.0922.The input waveform has the same orientation compare to the output waveform.

 After that we used the voltage divider circuit block and used a multimeter tomeasure the output voltage. In rotating the potentiometer counter clockwise andclockwise, we obtained an output voltage that ranges from 2.645V up to -2.664V. after 

that we added two-post connector that made out output voltage range decreased. Itbecame 0.48V to -0.498V.

Using a two-post connector, it decreased the range of our output voltage. Thismeans that by adding a load in series with the output terminal, it will have a voltage dropacross the load.

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Conclusion:

• An operational amplifier is a very close approximation to a perfect amplifier withan infinite gain. In reality op-amps do not quite attain perfection, but with gainsoften in the region of 100 000 or more, they are sufficiently close!

• An op amp is an electronic device, which provides a voltage output based on thevoltage input

• Non-inverting input: It is found that a positive voltage applied to the non-inverting input will produce a positive swing at the output.

• Inverting input: A positive voltage applied to the inverting input will produce anegative swing at the output.

• Op-amp has two inputs that connect to two terminals and one output

• There are 4 different types of packaging for an op amp. These are TO-5 Metal“Can” (8-pin), Flat-pack (10-pin), DIP (14-pin) and MINI-DIP (8-pin).

• Pin 1 and pin 5 are offset null, pin 2 is for inverting input and pin 3 is for non-inverting input, pin 6 is the output, pin 7 is for positive supply terminal and pin 4 isfor the negative supply terminal and pin 8 is not connected.

• Open-loop mode refers to the absence of a feedback loop from the output to theinput

• inverting amplifier inverts and scales the input signal

• non-inverting amplifier makes the positive input remains a positive output.

• The range of output voltage without the two-post connector is greater than therange of output voltage with the two-post connector because once you add aload in series with the output, there would be a voltage drop across it.

• Offset Nulling nullify the voltage in between the inputs and has the ability tocontrol the output voltage and it was observed that the potentiometer is adjustedduring this offset nulling process.

• With the use of negative supply voltage linked to a trimmer, the voltage inbetween was nullified and can control the output voltage.

• Many OP-AMPs have two pins labeled OFFSET NULL. When both inputs areconnected to the same voltage, the output should be zero.

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References:

http://www.google.com.ph/url?sa=t&rct=j&q=define+lf441&source=web&cd=4&ved=0CDoQFjAD&url=http%3A%2F%2Fwww.labvolt.com%2Fdownloads%2Fdownload%2F91571-00_OperationalAmplifierFundamentals_SW_ED4_PR2_web.pdf&ei=y0mfT-

vbD62UiQe5sq32Dw&usg=AFQjCNExKRIJwd3sW3qkxRmo-dLAC1AE-g&cad=rja

http://www.technologystudent.com/elec1/opamp2.htm

http://en.wikipedia.org/wiki/Attenuator_%28electronics%29

http://www.slideserve.com/Ava/chapter-5-operational-amplifiers

http://www.interfacebus.com/Glossary-of-Terms-offset-null-adjusment.html