This is the last part of some lab work I am undertaking. Attached is a photo of the lab script. In the attachment is the circuit image and the questions.
The last two questions are trivial, naturally the difficulty I am having is in the brunt of (a).
Prerequisites
We havn't had a formal introduction to transistors yet, so we have been told to ignore that part and were given a simple description of what it is doing. We have been given a formula for regulation and for calculating the average value of a rectified waveform and another one for calculating voltage ripple.
Attempt
(a) is basically asking us to find the values of R1, R2, and R3.
The op-amp is operating as a comparator, taking a fraction of the output in as negative feedback.
To find R1, I have:
\(v_o=i_{z1}R_1\)
\((5-3.3)=(5\times 10^{-3})R_1\)
\(\therefore R_1=340\Omega\)
To find R1 and R2, I am using:
\(v_o=v_i(1+\frac{R_2}{R_3})\)
Sometimes I understand that it's ok to pic an arbitrary value for one resistor (and rearrange for the other) as long as it lies within a certain region. In this case I have no idea what that region is. Is it ok to pic an arbitary value for R2 and find R3, or should I consider something when deciding a value for R2?
- Jim
The last two questions are trivial, naturally the difficulty I am having is in the brunt of (a).
Prerequisites
We havn't had a formal introduction to transistors yet, so we have been told to ignore that part and were given a simple description of what it is doing. We have been given a formula for regulation and for calculating the average value of a rectified waveform and another one for calculating voltage ripple.
Attempt
(a) is basically asking us to find the values of R1, R2, and R3.
The op-amp is operating as a comparator, taking a fraction of the output in as negative feedback.
To find R1, I have:
\(v_o=i_{z1}R_1\)
\((5-3.3)=(5\times 10^{-3})R_1\)
\(\therefore R_1=340\Omega\)
To find R1 and R2, I am using:
\(v_o=v_i(1+\frac{R_2}{R_3})\)
Sometimes I understand that it's ok to pic an arbitrary value for one resistor (and rearrange for the other) as long as it lies within a certain region. In this case I have no idea what that region is. Is it ok to pic an arbitary value for R2 and find R3, or should I consider something when deciding a value for R2?
- Jim
Attachments
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