MT-209

Mini Tutorial
MT-209
One Technology Way • P.O. Box 9106 • Norwood, MA 02062-9106, U.S.A. • Tel: 781.329.4700 • Fax: 781.461.3113 • www.analog.com
Dual Amplifier Band-Pass
(DABP) Filter
OUT
R4
R5
by Hank Zumbahlen,
Analog Devices, Inc.
C
R3
R2
IN THIS MINI TUTORIAL
R1
IN
The dual amplifier band-pass filter is used in high Q and
high frequency designs. This filter is one of a set of discrete
circuits incorporating op amps described in a series of mini
tutorials.
10414-002
C
Figure 2. Dual Amplifier Band-Pass Filter Design Equations
The dual amplifier band-pass filter structure is useful in designs
requiring high Qs and high frequencies. Its component sensitivity is small, and the element spread is low. A useful feature of
this circuit is that the Q and resonant frequency can be adjusted
more or less independently.
Referring to Figure 1, the resonant frequency can be adjusted by
R2. R1 can then be adjusted for Q. In this topology, it is useful
to use dual op amps. The match of the two op amps lowers the
sensitivity of Q to the amplifier parameters.
VO
V IN
 2 

s 
 R1 C 
=
 1 
1
 +
s 2 + s 
R
C
1
R
R
2
3C2


Choose C, R4.
Then, R5 = R4.
R=
1
2 π F0 C
R1 = Q R
OUT
R 2 = R3 = R
R4
R5
For gains <2 (gain = AV):
C
R3
R2
R1A
R2
C
10414-003
R1B
C
10414-001
IN
IN
R1
Figure 1. Dual Amplifier Band-Pass Filter
Note that the DABP has a gain of 2 at resonance. If lower gain
is required, Resistor R1 may be split to form a voltage divider.
This is reflected in the addendum to the design equations of the
DABP (see Figure 2).
+ Hω 0 S
s 2 + αω 0 s + ω 0 2
Rev. 0 | Page 1 of 2
R1A =
2 R1
AV
R1B =
R1A AV
2 − AV
MT-209
Mini Tutorial
REFERENCE
Zumbahlen, Hank. Linear Circuit Design Handbook. Elsevier. 2008. ISBN: 978-7506-8703-4.
REVISION HISTORY
3/12—Revision 0: Initial Version
©2012 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
MT10414-0-3/12(0)
Rev. 0 | Page 2 of 2