electronic amplifier design (2nd attempt)

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

  1. rjnachshin

    Thread Starter New Member

    Nov 10, 2015
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    Hi for my electronics class we were asked to design a circuit that meets the following requirements.
    Zi greater than 47k
    Zo has a max of 4.7k
    the overall no load voltage gain is over 1000
    the output voltage capacity is at least a 5v p-p with no visible distortion at 5v p-p input
    Vcc = 15v

    I designed the following circuit but I'm still having trouble picking the values for the capacitors and If my design meets the qualifications. I'm attaching the circuit. Im using a beta of 150 and a ro of 50k. Any feed back would be very helpful!!! If you have a better idea for how to approach the problem also please let me know.

    Thank You
     
    Last edited: Nov 11, 2015
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    :confused: That implies a voltage gain of at least 1, not "over 1000". Are you missing an "m" somewhere?
     
  3. marcf

    Member

    Dec 29, 2014
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    Yes, think you meant 5mVac for the input.

    In order for 4.1k (not a standard value try 4.3k) to drop 7.5v in order to put the amp into its most linear operation, you need to have 1.8mA of collector current. With a current gain of 150 you need at least 1.8ma/150 (120uA) of base current. There is no way you are going to obtain this with a 9.48Meg (not a standard value) resistor. (15v/9.48M = 1.5uA) At 1.8ma, the 330 ohm resistor would drop a little over 0.6v. The input impedance of the amp is about 50K. (150*330ohms) in parallel with 900K (not a standard value).

    This is pretty close to your goal of 47k.
     
  4. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    Pick a series, like E24 for your design.
     
  5. rjnachshin

    Thread Starter New Member

    Nov 10, 2015
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  6. rjnachshin

    Thread Starter New Member

    Nov 10, 2015
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    I have made my third design and his one has met the required goals!...well i think it did from my simulation. I need to find the parts electrical values, and the secondary rating like like power rating for resistors and voltage rating for capacitors. Also i need reference designators which I'm not sure what that means also. But I'm attaching my new design and the output waveform
     
  7. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    It will be hard to spec. capacitor values with unknown frequency
    For 100 Hz, might aim for 3 uF for input, which is odd value so best choice 4.7 uF to 5 uF. @ 25 V or better.
     
  8. hobbyist

    Distinguished Member

    Aug 10, 2008
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    Could you please show us the method you used to determine the values of your bias resistors.
     
  9. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    Output 5v peak to peak and a gain of 1000 means the input is 5V peak to peak / 1000 or 5 mV peak to peak.

    Your diagram has a signal generator at 2.5 mV rms or 7.07 mV peak to peak.
     
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