Cutoff Freq of Inverting Op Amp

Discussion in 'Homework Help' started by KevC, Jan 15, 2012.

  1. KevC

    Thread Starter New Member

    Jan 15, 2012
    2
    0
    Hi guys,

    The question I need help with is
    "Determine the maximum gain possible that meets the high-frequency roll-off specification of fH = 20 kHz."

    http://i44.tinypic.com/ezlo2x.png

    As you can see from my schematic & bode plot, I designed the roll-on to be at 100Hz and it rolls off at 815kHz.

    How do I mathematically find the bandwidth or the cutoff frequency? I understand that to find the roll-on you simply do 1/(2piR2C1). I assume that once I find out how to find cutoff freq, I can design the roll-off at 20kHz and find the gain.

    Thank you,

    KC
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,006
    3,232
    Do you understand the "gain-bandwidth product" specification of op amp amplifiers? It's determined by the internal frequency response of the op amp, not the external components. If you understand that (Google if needed) then you can answer your own question.
     
    KevC likes this.
  3. 2010ee179

    New Member

    Jul 1, 2011
    12
    1
    For a single OP-AMP you just need to know gain bandwidth product...
    For cascaded OP-AMPS frequency response...
    May be you should read this:

    http://www.4shared.com/office/6PK1xm21/opamp_cascade.html?

    Gain bandwidth product (Google it) is also specified as fT (transition frequency)...It is given in data sheets.
     
    KevC likes this.
  4. KevC

    Thread Starter New Member

    Jan 15, 2012
    2
    0
    Thank you guys. I didn't understand GBP before and now I do!
     
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