· PROCEDURE Build the circuit depicted below in Figure 3. +15V 2 741 6 0 5 -15V

Question

· PROCEDURE Build the circuit depicted below in Figure 3. +15V 2 741 6 0 5 -15V Figure 3: Measuring circuit for the Voltage Offset Adjustment Range MEASUREMENTS Measure and record the range in value of Vo as the 10kS2 potentiometer is varied from the full counter clockwise to the full clockwise position. at full counter clockwise) = 0. Vo (at full clockwise) = NOTE: You can also try to find the matching point of the potentiometer so that Vo-Vos 0 V (in the next experiment we will need to find this point) Don't disassemble this circuit for now, you only need to do some minor adjustments in the next part. ANALYSIS As we can see from our measurements in part one, the input offset voltage is relatively small (though dependent on temperature). Nevertheless, why is it so important to be aware of the input offset voltage. Imagine an op amp configuration with a closed loop gain of 1000 and an input offset voltage of 5 mV, what would be the impact on our output voltage Vo?

Explanation / Answer

input offst voltage is error in op amp, output of an op amp should be zero when no input is applied but in practical due to manufacturing process output is not zero and that error is known as input offset voltage.

Input offset voltage is to be ignored for a small gain as it will not be of much significance in output.

With

gain A = 1000  

i/p offset voltage = 5 mV

so it will effect Vo it will be multiplied by 1000

new Vo = Vo + 1000 * 0.005 = Vo + 5

will cause a big error in output

  

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