S ll K hit tSallen-Key architecture bandpass filterp

April 29, 2009 : Sani Hadziahmetovic p 9, 9

ECE 262 PROJECT PROPOSAL

ABSTRACTABSTRACT

Thi j t i t i l t d l t S ll k hit t This project aims to simulate and layout a Sallen‐key architecture bandpass filter with ‐3dB bandwidth from 1MHz to 2MHz. The Sallen‐key architecture will implement a double pole Butterworth response using a unity gain op amp to achieve a sharp knee at the p g y g p p pcutoff frequencies.

Block Diagram 1Block Diagram 1

Th i bl k di f S ll K hThe gain block diagram of a Sallen‐Key arch.

The ideal transfer functionThe ideal transfer function

Block Diagram 2Block Diagram 2

Circuit EstimatesHigh pass Stage Low pass StageHigh-pass Stage Low-pass Stage

C1,C2 = 9 pF R3,R4 = 12.5 k ΩR1 = 12 5 kΩ C3 = 9 pFR1 = 12.5 kΩ C3 = 9 pFR2 = 25 kΩ C4 = 6 pF

OTA SchematicOTA Schematic

Filter SchematicFilter Schematic

OTA SimulationOTA Simulation

66 dB pass band magnitude response

135.21* phase angle at -3dB

Lowpass SimulationLowpass Simulation

Sharp attenuation kneeActual ‐3dB cutoff f = 2 19 MHzActual 3dB cutoff f = 2.19 MHz‐84.512* phase angle at ‐3dB

Highpass SimulationHighpass Simulation

‐4 9 dB at 1MHz‐4.9 dB at 1MHz

OTA LayoutOTA Layout

Filter LayoutFilter Layout

W = 1124.57 umL = 1058 57 umL = 1058.57 umTotal Area = 1. 19 cm2

Design ChallengesDesign Challenges

OTA h OTA phase response

Need large values of C

Sallen‐key architecture begins to fail at high freqs. (dependent on GB of the opamp)q p p p