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How to design 2decade BJT-OPAMP cascade inverting voltage amplifier?

  1. Mar 17, 2008 #1
    Can somebody help me to find this kind of circuit.im really appreciete your help

    Specification
    Only one bjt,one opamp ua741 and asingle power supply of 12v must be used. A 10k ohm load and an input signal will be connected via capacitors to the amplifier. The max voltage gain is about -500.imput impedance is about 600 ohm.output impedance is about 10k ohm.the low cut off frequency is about 200hz and the high cutoff frequency is about 20khz(bandwith of 200-20khz ;2decades).the maximum pek-to-peak(mpp) output voltage without clipping is more or equal to 6v.make sure that the opamp must not produce a low rate distortion at less or equal 20khz.
    Please I need this for final year project
     
  2. jcsd
  3. Mar 17, 2008 #2

    berkeman

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    Staff: Mentor

    Thread moved from EE to Homework Help.

    Welcome to the PF, badrie. Can you show us your initial approach to this question? What can you tell us about common connection diagrams for opamps in the inverting configuration? Do you have an idea where they want you to use the BJT?

    Also, could you double-check the specifications -- specifically the output impedance. A Zout of 10k Ohms sounds like a typographical error....
     
  4. Mar 17, 2008 #3
    TQ bekeman for your reply.
    for your information i need to design this circuit so that i can get the output like in specification.that means that i need to prove that my circuit can be produce same output that in question.this circuit just need to prove the output.

    for ur information,i dont know how to connect between opamp and the bjt. that y i need some idea from u.yeah the output impedance is 10k OHM.

    i already do some the research. but i only get "2decade BJT cascade inverting voltage amplifier". this circuit use two bjt.i do appreciate if u give me some idea how to change it into "one BJT and one ua741(opamp)
     
  5. Mar 17, 2008 #4

    berkeman

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    Staff: Mentor

    Show us your circuit with 2 BJTs and the opamp.

    Also, here's a Quiz Question -- why do you need a BJT at all, given these specifications? There's one specification (and one corresponding graph in the 741 datasheet) that would be the only reason that it would be used here.....

    Remember, we will not do the work for you. We can offer tutorial assistance. What courses in opamps and transistors have you taken to support your work on this "senior project"?
     
  6. Mar 18, 2008 #5
    tq bekeman..
    when i read about ur reply, it force me to open again my electronic book.since i majoring in electronic,so i have to refresh back my knowledge.

    i already got the circuit and try it using PSpice.i juz need to do some touch up to meet the specification

    actually i really dun understand why i need to prove the output.i already read the 741 data sheet and it already show all the specification.

    anyway tq for ur assistance.i appreciete it. hope u delight to help me.
     
  7. Mar 18, 2008 #6

    berkeman

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    Staff: Mentor

    No, there is at least one specification in your assignment that is not met by just the 741 alone. Hint -- two 741s in series would be able to meet the specification.

    Another hint -- why does the 2 BJT circuit use a cascode configuration? The answer is related.
     
  8. Mar 18, 2008 #7
    ok..i understand that.

    i got some idea how to connect 741 and the bjt. about using two 741 idea is correct.i no doubt about it.but i only need to use one opamp. i will work on it more. tq.wish me luck
     
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