OPA690IDBVT datasheet(17/37 Pages) TI1

17 / 37 page

OPA690

1.5kW

432W

137W

500W

1.87kW

+5V

DIS

0.1 F

150pF

0.1 F

100pF

5MHz,2nd-Order

ButterworthFilter

Frequency(Hz)

5MHz,2nd-OrderButterworthFilterResponse

100k

10M

-5

OPA690

www.ti.com

SBOS223F – DECEMBER 2001 – REVISED FEBRUARY 2010

SINGLE-SUPPLY ACTIVE FILTERS

both the input and output pins. The midband signal

gain is set to +4 (12dB) in this case. The capacitor to

The high bandwidth provided by the OPA690, while

ground on the noninverting input is intentionally set

operating on a single +5V supply, lends itself well to

larger to dominate input parasitic terms. At a gain of

high-frequency active filter designs. Again, the key

+4, the OPA690 on a single supply will show ~80MHz

additional requirement is to establish the dc operating

small-

and

large-signal

bandwidth.

The

resistor

point of the signal near the supply midpoint for

values have been slightly adjusted to account for this

highest dynamic range. See Figure 42 for an example

limited bandwidth in the amplifier stage. Tests of this

design of a 5MHz low-pass Butterworth filter using

circuit show a precise 5MHz,

−3dB point with a

the Sallen-Key topology.

maximally

flat

passband

(above

the

32kHz

ac-coupling corner), and a maximum stop band

Both the input signal and the gain setting resistor are

attenuation of 36dB at the amplifier’s

−3dB bandwidth

ac-coupled using 0.1mF blocking capacitors (actually

of 80MHz.

giving bandpass response with the low-frequency

pole set to 32kHz for the component values shown).

As discussed for Figure 37, this allows the midpoint

bias formed by the two 1.87k

Ω resistors to appear at

Figure 42. Single-Supply, High-Frequency Active Filter

Product Folder Link(s): OPA690

OPA690IDBVT Datasheet(PDF) 17 Page - Texas Instruments

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