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# May 2023 StudentZone Quiz Solution

Question 1:

Using the values and formulas provided in the laboratory directions compute the following parameters:

• Forward current through the IR LED. (use datasheet of the QED-123)
• Cut-off frequency of the high-pass filter.
• Cut-off frequency of the second stage low-pass filter.
• Cut-off frequency of the third stage low-pass filter.
• Gain of the third stage amplifier

• Forward current through the IR LED can be computed using the following forumla (the datasheet value for the forward volage of the QED-123 is 1.7V):

IF = 7mA

• Cut-off frequency of the high-pass filter can be computed using the following formula:

Fc1 = 0.33Hz

• Cut-off frequency of the second stage low-pass filter can be computed using the following formula:

Fc2 = 3.3Hz

• Cut-off frequency of the third stage low-pass filter can be computed using the following formula:

Fc3 = 3.3Hz

• Gain of the third stage amplifier

AV = - 470

Question 2:

What parameters change if R5 is modified?

If R5 is modified, this will affect the gain of the third stage amplifier.

Question 3:

What parameters change if R6 is modified?