What is the purpose of using trimmer potentiometer in operational amplifier circuit....?

Question

Related to electronics experiment

Answer 1

A differential amplifier is a type of an electronic amplifier that multiplies the difference between two inputs by some constant factor (the differential gain). By using a potentiometer instead of resistors in the circuit, you can adjust the gain of the amplifier.

Answer 2

a potentiometer consists of a resistor (A to B) and a wiper arm(C)

..A----/\/\/\/\/\/\/----B
.............. ^
.............. |
..............C
(ignore the .'s)

may beconnected in one of two ways.

A.) As a variable resistance (single resistance) Connect C to either A or B
B.) As a variable Voltage divider (dual resistance) Connect A & B to voltage and develope a proportional voltage on C

Depending on there number in use,placement and connection in an Op Amp circuit they may be used for the following:

1.) Feedback control - i.e. Gain Adjustment
2.) Offset adjustment
3.) Hystersis control
4.) Compensation of resistance tolerances
5.) Volume control - adjustment of input voltage
6.) Voltage adjustment on an input either the + or - for use as a comparator

Answer 3

You means besides as a volume control ? It's also used as a variable resistor that allows to to adjust the gain as needed as not all parts produce the exact same results, and allows you to compensate for that fact without have to always replace a fixed resistor. Besides when you experiment, having a trivariable resistor allows you to see what the different effects it has on your circuit with only one part.

Answer 4

The answer that I think you are looking for is a combination of a couple of the answers above mine.

There are three things that are frequently "trimmed" in an op-amp circuit. Taking them in the order that you are most likely to encounter them in learning about electronics and op-amps they are:

(1) Gain
(2) Input Offset
(3) Signal Offset

(1) Gain: Imagine a simple multiplier circuit where the input voltage comes into the "+" input of the op-amp, and the output of the op-amp goes to a voltage divider to ground made up of two equal value resistors -- call them 10K each -- and the center of that voltage divider is connected to the "-" input of the op-amp. As the input voltage goes positive to +1 volt for example, the output of the op-amp is driven positive until it reaches a high enough voltage that the tap-off point of the voltage divider is equal to the input voltage: the output drives to +2 volts, the voltage divider divides this by 2 and thus feeds +1 volt back to the "-" input and so as a result you get a voltage-multiplied-by-2 circuit. But in reality resistors are not exactly "10K" values -- they are typically the specified value plus or minus 5 percent (so 9.5K to 10.5K). Therefore, you don't get exactly 2:1 multiplication, but somewhere between 1.9:1 to 2.1:1. To correct for these resistor value tolerances, the circuit is instead built with a trim pot between the two resistors. Typically the two resistors will be decreased by 10% and a trim pot equal to 20% of the resistance value is added, and the signal to the "-" input of the op-amp is now taken from the wiper of the trim pot. In this way, the trim pot can be adjusted so that the "-" input is connected to a point that is EXACTLY halfway between the op-amp's output and ground, allowing you to trim the circuit to exactly a 2:1 amplification.

(2) Input Offset: Imagine a basic voltage-follower circuit, where the incoming signal is connected to the "+" input of the op-amp, and the op-amp's output is feed back to the "-" input. Whatever the input voltage is, the output voltage matches it exactly IN THEORY. But in reality, the two inputs are a bit different from each other because the transistors inside the op-amp are slightly different -- if your input signal were exactly zero volts, the output will be plus a few millivolts to minus a few millivolts as a result. In this case, you use a trim pot to add or subtract a bit of current or voltage to one of the inputs in order to "null the offset" and get zero volts out for zero volts in.

(3) Signal Offset: This is when you have a signal coming in that consists of some variable voltage plus a fixed offset, and you want to take that fixed offset out of the signal. Imagine a system where the incoming signal is composed of a data signal of plus 8 volts to minus 8 volts, sitting on a fixed offset of plus 12 volts. That means the incoming signal is anywhere from +4 volts to +20 volts. You want to convert this to a signal that is negative 8 volts to positive 8 volts. You need to pass it through an op-amp circuit that removes the +12 volt offset (a circuit called a "level shifter"). The circuit is a bit more complex than I want to describe in writing (you can see it in the second link below) but you can imagine that just like the case where we wanted to trim the gain to exactly 2:1, in this circuit we need to trim the offset to exactly -12 volts.

If you can provide a link to the exact experiment, I will be happy to tell you what the trim pot in question is doing.

Answer 5

Potentiometer Purpose

Answer 6

Op-amps are very versatile ICs. i'm specific circuits with with greater desirable than 4 could be subject-loose. Radio shack could have books approximately op-amps. LEDs are very useful and can be exciting to paintings with.

Answer 7

to make the amplicifaction variable