Difference between revisions of "GradFinalLab RS"

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we can use the approximate formula to calculate the threshold voltages:
 
we can use the approximate formula to calculate the threshold voltages:
  
1) if the output is high:
+
1) if the output is high:
 +
 
 
  <math>V_2 \cong \frac{V_{ref}}{2} + \frac{R}{2R_3}V_{cc}</math>
 
  <math>V_2 \cong \frac{V_{ref}}{2} + \frac{R}{2R_3}V_{cc}</math>
  
2) if the output is low:
+
2) if the output is low:
 +
 
 
  <math>V_2^' \cong \frac{V_{ref}}{2} - \frac{R}{2R_3}V_{cc}</math>
 
  <math>V_2^' \cong \frac{V_{ref}}{2} - \frac{R}{2R_3}V_{cc}</math>
 +
  
 
Let's calculate the thresholds voltages using the actual values used elements:
 
Let's calculate the thresholds voltages using the actual values used elements:

Revision as of 05:25, 26 April 2011

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Construct a Schmitt Trigger using the 741 Op Amp

Draw the Schmitt Trigger circuit you constructed. Identify the values of all components

Schmitt trigger 01.png

To construct the circuit above I am going to use the following components and voltages:

  1. [math]R_1 = R_2 = 1\ k\Omega[/math]
  2. [math]R_3 = 10\ k\Omega[/math]
  3. [math]\mbox{OP}\ \mbox{AMP}\ 741[/math]
  4. [math]V_{ref} = V_{cc} = 15\ V[/math]

Graph [math]V_{out}[/math] as a function of [math]V_{in}[/math]. Is there a hysteresis loop?

Identify the input voltage threshold levels at which a [math] V_{in}[/math] will produce [math]V_{out} \approx V_{cc}[/math]

Because

[math]R = R_1 = R_2 = 1\ k\Omega \ll R_3 = 10\ k\Omega[/math]

we can use the approximate formula to calculate the threshold voltages:

1) if the output is high:

[math]V_2 \cong \frac{V_{ref}}{2} + \frac{R}{2R_3}V_{cc}[/math]

2) if the output is low:

[math]V_2^' \cong \frac{V_{ref}}{2} - \frac{R}{2R_3}V_{cc}[/math]


Let's calculate the thresholds voltages using the actual values used elements:

[math]V_2 \cong \frac{V_{ref}}{2} + \frac{R}{2R_3}V_{cc} = [/math]
[math]V_2^' \cong \frac{V_{ref}}{2} - \frac{R}{2R_3}V_{cc} = [/math]

Compare the threshold values to what is expected.

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