The value of R

Ω.

The last step in this design is setting the amplifier’s −3db

band magnitude variation limit, the low frequency response

must extend to at lease one−fifth the lower bandwidth limit

and the high frequency response must extend to at least five

times the upper bandwidth limit. The gain variation for both

limit. The results are

f

(8)

and

f

(9)

As stated in the External Components section, both R

conjunction with C

ters. Thus to obtain the desired low frequency response of

eration. The combination of two single order filters at the

same frequency forms a second order response. This results

in a signal which is down 0.34dB at five times away from the

single order filter −3dB point. Thus, a frequency of 20Hz is

used in the following equations to ensure that the response

is better than 0.5dB down at 100Hz.

C

i

≥ 1/(2π*20kΩ*20Hz) = 0.397µF; use 0.39µF (10)

The high frequency pole is determined by the product of the

desired high frequency pole, f

A

resulting GBWP = 150kHz which is much smaller than the

LM4917’s GBWP of 3MHz. This figure displays that if a

designer has a need to design an amplifier with a higher

gain, the LM4917 can still be used without running into

bandwidth limitations.

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