LTC1014
Linear Technology
ACTIVE (OP-AMP) STATE VARIABLE ... 3/4 LTC1014
Application NoteAnalog
Application Note 27A: A Simple Method of Designing Multiple Order All Pole Bandpass Filters by Cascading 2nd Order Sections
A guide for designing high-order bandpass filters by cascading 2nd-order sections using LTC switched capacitor filters. Covers Butterworth and identical section methods.
Overview
This application note describes two primary methods for designing high-order, all-pole bandpass filters using universal switched capacitor filters such as the LTC1059, LTC1060, LTC1061, and LTC1064. The first method utilizes the traditional cascading of non-identical 2nd-order sections to create Butterworth and Chebyshev filter responses, supported by normalization tables to simplify the design process. The second method involves cascading identical 2nd-order sections, which simplifies mathematical calculations and hardware implementation. The document includes step-by-step design examples, hardware implementation details for various operational modes (Mode 1, Mode 2, and Mode 3), and a comparison between switched capacitor and active RC state-variable topologies. It also highlights the advantages of switched capacitor filters, including high center frequency accuracy and the elimination of precision film capacitors.
Use Cases
- High-order analog filter design
- Single frequency tone detection
- Signal noise and interference rejection
- Switched capacitor circuit implementation
- Analog signal processing
Topics
bandpass filters
switched capacitor filters
LTC1059
LTC1060
LTC1061
LTC1064
Butterworth filters
Chebyshev filters
filter cascading
2nd order sections
LTC1014
Referenced Parts
LTC1059
Linear Technology
LTC’s switched capacitor filters (LTC1059, LTC1060, LTC1061,LTC1064) to be utilized as high quality bandpass filters.
LTC1059A
Linear Technology
For instance, an LTC1059A, 2nd order universal filter, has a guaranteed initial center frequency tolerance of ±0.3%.
LTC1060
Linear Technology
We start with two 2nd order sections (1 LTC1060, 2/3 LTC1061 or 1/2 LTC1064)
LTC1061
Linear Technology
We start with two 2nd order sections (1 LTC1060, 2/3 LTC1061 or 1/2 LTC1064)
LTC1064
Linear Technology
We start with two 2nd order sections (1 LTC1060, 2/3 LTC1061 or 1/2 LTC1064)
LTC1060A
Linear Technology
the “A” versions of the LTC1059, LTC1060, LTC1061 or LTC1064 should be specified.
LTC1061A
Linear Technology
the “A” versions of the LTC1059, LTC1060, LTC1061 or LTC1064 should be specified.
LTC1064A
Linear Technology
the “A” versions of the LTC1059, LTC1060, LTC1061 or LTC1064 should be specified.
| LTC1014 | Linear Technology | ACTIVE (OP-AMP) STATE VARIABLE ... 3/4 LTC1014 |
| LTC1059 | Linear Technology | LTC’s switched capacitor filters (LTC1059, LTC1060, LTC1061,LTC1064) to be utilized as high quality bandpass filters. |
| LTC1059A | Linear Technology | For instance, an LTC1059A, 2nd order universal filter, has a guaranteed initial center frequency tolerance of ±0.3%. |
| LTC1060 | Linear Technology | We start with two 2nd order sections (1 LTC1060, 2/3 LTC1061 or 1/2 LTC1064) |
| LTC1061 | Linear Technology | We start with two 2nd order sections (1 LTC1060, 2/3 LTC1061 or 1/2 LTC1064) |
| LTC1064 | Linear Technology | We start with two 2nd order sections (1 LTC1060, 2/3 LTC1061 or 1/2 LTC1064) |
| LTC1060A | Linear Technology | the “A” versions of the LTC1059, LTC1060, LTC1061 or LTC1064 should be specified. |
| LTC1061A | Linear Technology | the “A” versions of the LTC1059, LTC1060, LTC1061 or LTC1064 should be specified. |
| LTC1064A | Linear Technology | the “A” versions of the LTC1059, LTC1060, LTC1061 or LTC1064 should be specified. |