# Electronic Design Problem (initial design).

Discussion in 'Homework Help' started by rjnachshin, Nov 11, 2015.

1. ### rjnachshin Thread Starter New Member

Nov 10, 2015
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For my electronics class we were assigned a design problem given the following specifications. We had to design a amplifier that at 1kHz would have VCC of 15v, a Zi of 47k min and Zo of 4.7k max. It also needed a overall no load gain of over 1000 and the output voltage needs a capacity of at least 5v p-p. This is my design so far using Beta as 300 and Ro as 4.5k.

My questions are will it work and also what improvements can I make to help build a better circuit. This is my first design problem so any response is helpful! I attached my circuit. I will add capacitors on both 12.8K resistors but i'm not sure what value capacitors to use for them/rest of circuit.

2. ### MrAl Distinguished Member

Jun 17, 2014
2,573
523
Hi,

You have a 1Hz input there? Or is it supposed to be 1kHz?

The input capacitor may be too small for 1Hz. Did you check the approximate 3db cutoff point of the input section using that capacitor value?

3. ### rjnachshin Thread Starter New Member

Nov 10, 2015
12
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It supposed to be 1kHz I'm sorry. I don't know how to check db cutoff or really how to choose what capacitor value to use to be quite honest.

Nov 10, 2015
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5. ### Jony130 AAC Fanatic!

Feb 17, 2009
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Have you check the gain of your amp ? Because now the gain will be "very low".
Is this has to be a two stage amp? Or you could use more stages ??

6. ### rjnachshin Thread Starter New Member

Nov 10, 2015
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I can use as many stages as i want but i calculated the gain to be very high using equations i used in class, however that is with ought using the capacitors and AC values since we never learned that...

7. ### Jony130 AAC Fanatic!

Feb 17, 2009
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Can you show us this equations?

Nov 10, 2015
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9. ### rjnachshin Thread Starter New Member

Nov 10, 2015
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These are my calculations.

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10. ### Jony130 AAC Fanatic!

Feb 17, 2009
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Aha, so you already include the capacitor in your calculation. Good for you.
As for the cap size
Ce ≈ 1/(2* pi *F* re) ≈ 0.16/(F*re)

11. ### panic mode Senior Member

Oct 10, 2011
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your input signal and power source do nothing, you need to complete circuit.

12. ### rjnachshin Thread Starter New Member

Nov 10, 2015
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There going to be connected to ground but I'm not sure what to make my ac voltage.