# oscillating circuit

Discussion in 'Homework Help' started by waco3002, May 12, 2015.

1. ### waco3002 Thread Starter New Member

May 12, 2015
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a. The resistor and capacitor values required, for the oscillator to resonate at 250 MHz

using formula Fr = 1 / (2(pi)RC)

R = 0.21221

C = 3*10^-9

I have done this first bit answers above. but don't know where to start on the next bit

b. The output voltage of the oscillating circuit if the input voltage is 250mV/30^o

any help would be appreciated.

2. ### Jony130 AAC Fanatic!

Feb 17, 2009
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But we need to see a circuit diagram.

Papabravo likes this.
3. ### Papabravo Expert

Feb 24, 2006
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I don't believe you can make an RC oscillator at 250 MHz, and the value of the resistor is ridiculously low.

I'm not familiar with the meaning of 250mV/30^o. I'm good up to the /, but what is the crap that follows?

4. ### waco3002 Thread Starter New Member

May 12, 2015
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sorry haven't done this before. please see pdf of question and diagram.

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5. ### ScottWang Moderator

Aug 23, 2012
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I'm not sure you want to create a new history or magical, almost the RC frequency less than 10Mhz and more than 100Khz may appear a astable phenomenon.

Are you just playing with a formula or really want to make some stuffs?

6. ### ScottWang Moderator

Aug 23, 2012
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That is only a filter not a oscillator.

7. ### waco3002 Thread Starter New Member

May 12, 2015
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im not making anything this is just an assignment from college.

8. ### Papabravo Expert

Feb 24, 2006
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Where did the capacitor value come from? It is not in the problem statement. You must realize that your solution is not unique.
Did they give you a circuit diagram of a Wein-Bridge?
http://en.wikipedia.org/wiki/Wien_bridge_oscillator

9. ### waco3002 Thread Starter New Member

May 12, 2015
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I just put a value in for the capacitor so i could calculate a value for the resistance.

where it refers to figure 4 that is the drawing in the pdf.

10. ### DickCappels Moderator

Aug 21, 2008
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May we please see figure 4?

11. ### Papabravo Expert

Feb 24, 2006
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Yes and that gave you an absolutely ridiculous resistor value. In a Wein-Bridge oscillator you will have some trouble finding an Opamp to work at those frequencies, but good luck.

12. ### waco3002 Thread Starter New Member

May 12, 2015
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the assignment question as given is here.

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13. ### Papabravo Expert

Feb 24, 2006
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The drawing in figure 4 is not an oscillator. It is not even a circuit. It is a fragment of a circuit.
If your instructor is too busy to ask reasonable questions I'd be asking for my tuition money back

14. ### DickCappels Moderator

Aug 21, 2008
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@Papabravo, I suspect that we are confused some problem with terminology.

15. ### Papabravo Expert

Feb 24, 2006
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Tha't fine but I actually suspect the 250 MHz., is a typographical error.

Apr 26, 2005
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