OPA320SAIDBVT datasheet(19/37 Pages) NSC

19 / 37 page

OUT

V = 1V

RMS

OPA320

150kW

19.5kW

220pF

1.8kW

3.3nF

47pF

V+

V-

1nF

150pF

549W

1.24kW

V+

OUT

V-

OPA320

OPA320, OPA2320

OPA320S, OPA2320S

www.ti.com

SBOS513E – AUGUST 2010 – REVISED JUNE 2013

ACTIVE FILTER

MFB and Sallen-Key, low-pass and high-pass filter

synthesis

quickly

accomplished

using

TI’s

The OPA320 is well-suited for active filter applications

FilterPro™ program. This software is available as a

that require a wide bandwidth, fast slew rate, low-

free download at www.ti.com.

noise, single-supply operational amplifier. Figure 45

shows a 500kHz, second-order, low-pass filter using

the

multiple

−feedback

(MFB)

topology.

The

components

have

been

selected

provide

maximally-flat Butterworth response. Beyond the

cutoff

frequency,

roll-off

–40dB/dec.

The

Butterworth

response

ideal

for

applications

requiring predictable gain characteristics, such as the

anti-aliasing filter used in front of an ADC.

One point to observe when considering the MFB filter

is that the output is inverted, relative to the input. If

this inversion is not required, or not desired, a

noninverting output can be achieved through one of

these options:

1. adding an inverting amplifier;

Figure 45. Second-Order Butterworth 500kHz

2. adding an additional second-order MFB stage; or

Low-Pass Filter

3. using a noninverting filter topology, such as the

Sallen-Key (shown in Figure 46).

Figure 46. OPA320 Configured as a Three-Pole, 20kHz, Sallen-Key Filter

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OPA320SAIDBVT Datasheet(PDF) 19 Page - National Semiconductor (TI)

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