Phototransistor modeled as a Thevenin equivalent circuit

597
0
1. The problem statement, all variables and given/known data
you have a phototransistor that you have modeled as a Thevenin equivalent circuit. It has a output impedence(Thevenin Impedence) of 10kohm and produces a peak voltage o2 2V at a frequency of 80 MHz. The input impedence of the oscilloscope as this simple combination of input impedences.
a.draw the osilloscope/photodetector circuit
b. calculate the half power frequency
c. a 50 ohm resistor is added in parallel to the 1M ohm load. draw the new circuit.
d. calculate the new break frequency.


2. Relevant equations
[tex]f_b=\frac{1}{2\Pi R C}[/tex]



3. The attempt at a solution
1.The photodetector in parallel with the capacitor and 1m ohm resistor
2. I just took [tex]f_b=\frac{1}{2*\Pi*10^3 ohms*20^-9F}=81.40MHz[/tex]
3.The photodetector in parallel with the capacitor,1m ohm resistor, and 50 ohm resistor
4. not too sure
 
4,209
1
Could you clear-up this typo?

"The input impedence of the oscilloscope as this simple combination of input impedences."
 
597
0
Sorry,
"Model the oscilloscope as this simple combination of input impedences."
 
597
0
Actually for b. I get 7.87 Hz.
 
597
0
Sooo......is that right?
 

The Physics Forums Way

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving
Top