MCP6281 datasheet(15/32 Pages) MICROCHIP

15 / 32 page

 2004 Microchip Technology Inc.

DS21811D-page 15

MCP6281/2/3/4/5

4.8.3.4

Buffered Non-inverting Integrator

Figure 4-12 shows a lossy non-inverting integrator that

is buffered and has a Chip Select input. Op amp A is

configured as a non-inverting integrator. In this config-

uration, matching the impedance at each input is

recommended. RF is used to provide a feedback loop

at frequencies << 1/(2

πR

1C1) and makes this a lossy

integrator (it has a finite gain at DC). Op amp B is used

to isolate the load from the integrator.

FIGURE 4-12:

Buffered Non-inverting

Integrator with Chip Select.

4.8.3.5

Inverting Integrator with Active

Compensation and Chip Select

Figure 4-13 uses an active compensator (op amp B) to

compensate for the non-ideal op amp characteristics

introduced at higher frequencies. This circuit uses

op amp B as a unity-gain buffer to isolate the integration

capacitor C1 from op amp A and drives the capacitor

with low-impedance source. Since both op amps are

matched very well, they provide a higher quality

integrator.

FIGURE 4-13:

Integrator Circuit with Active

Compensation.

4.8.3.6

Second-Order MFB Low-Pass Filter

with an Extra Pole-Zero Pair

Figure 4-14 is a second-order multiple feedback low-

pass filter with Chip Select. Use the FilterLab® software

from Microchip to determine the R and C values for the

op amp A’s second-order filter. Op amp B can be used

to add a pole-zero pair using C3, R6 and R7.

FIGURE 4-14:

Second-Order Multiple

Feedback Low-Pass Filter with an Extra

Pole-Zero Pair.

4.8.3.7

Second-Order Sallen-Key Low-Pass

Filter with an Extra Pole-Zero Pair

Figure 4-15 is a second-order Sallen-Key low-pass

filter with Chip Select. Use the FilterLab® software from

Microchip to determine the R and C values for the op

amp A’s second-order filter. Op amp B can be used to

add a pole-zero pair using C3, R5 and R6.

FIGURE 4-15:

Second-Order Sallen-Key

Low-Pass Filter with an Extra Pole-Zero Pair and

Chip Select.

VIN

VOUT

MCP6285

1C1

()C

VIN

VOUT

MCP6285

VIN

VOUT

MCP6285

VIN

VOUT

MCP6285

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