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frequency and transistors


jonathan.wood1
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I was just wondering if anyone here would mind helping me out with a problem. I have consulted with fellow classmates the net and texts. but have yet to figure out a way to calculate,
the unity-gain frequency of an op-amp with a closed loop gain of 3.7 and an upper critical frequency of 514.

nor the new upper critical frequency if the gain is changed to 5.7

I have really no idea the closest formula I've run into has ft=Acl*fc(cl) but Im missing information and not sure if this formula would work even if I had the required info.

Thanks,

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Hi Student,
Welcome to our forum.
Opamp manufacturers call the frequency where the response drops -3dB the cutoff frequency. Is it what you call "the upper critical frequency"?

Opamp manufacturers call the frequency where the gain is only 1 Unity Gain Bandwidth (National Semi and Texas Instruments) and Gain Bandwidth Product (Motorola).

The high frequency response of most opamps drops at exactly 6dB per octave which is also 20dB per decade of frequency, so it is easy to see the cutoff frequency at various gains on the curve on the datasheet.

Here is the cutoff frequency curve for a TL07x opamp: 

post-1706-14279143173355_thumb.png

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