9Q

=

1

C

4Q

0

1

Z

R

1)Q

9Q

2

=

2

R

1

R

2

4Q

2

R =

1

R

(

1 Q

K -

Q =

2

=

1

1

Q =

2

1

1

1

LMP8602, LMP8602Q, LMP8603, LMP8603Q

SNOSB36D – JULY 2009 – REVISED MARCH 2013

www.ti.com

For any filter gain K > 1x, the design procedure can be very simple if the two capacitors are chosen to in a

certain ratio.

(5)

Inserting this in the above equation for Q results in:

(6)

Which results in:

(7)

In this case, given the predetermined value of R1 = 100 k

Ω (the internal resistor), the quality factor is set solely

equation:

(8)

For the gain of 5 for the LMP8602 this results in:

(9)

For the gain of 10 for the LMP8603 this is:

(10)

For instance, the value of Q can be set to 0.5

√2 to create a Butterworth response, to 1/√3 to create a Bessel

last step of the design procedure is to calculate the required value of C to give the desired low-pass cut-off

frequency using:

(11)

Which for the gain = 5 will give:

(12)

and for the gain = 10:

(13)

16

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