201303.pdf 36567KB Mar 22 2013 09:11:22 PM

More documents

Recommendations

Info

designideas CLASSICS Originally published in the December 19, 1991, issue of EDN Filter quashes 60-Hz interference Adolfo A Garcia, Analog Devices, Santa Clara, CA ↘ The circuit in Figure 1 filters 60-Hz interference from lowfrequency, low-level signals. The filter exhibits 40-dB rejection (Q=0.75) and draws 95 μA max from a single-sided 5V supply. Resistors R 1 , R 2 , and R 3 and capacitors C 1 , C 2 , and C 3 form a classic twin-T section, and IC 1 and IC 2 provide local and global feedback. The frequency If addItIonal rejectIon Is needed, cascade fIlter sectIons. selectivity (Q) and the rejection performance of this active filter are very sensitive to the relative matching of the capacitors and resistors in the twin-T section. Table 1 shows rejection and Q as a function of the value of R Q . R 4 , R 5 , C 4 , and IC 3 form a very-lowimpedance reference source to bias IC 1 and the twin-T section to half the supply voltage. To configure the filter to operate at 60 Hz, choose a Q that will provide enough rejection without excessive loss of desired low-frequency signals that may be close to the filter’s notch frequency. The value of R Q is expressed as R Q =(4Q−2)R 7 . The gain of the output amplifier is simply that of a conventional noninverting amplifier: A=1+(R Q /R 7 )=4Q−1, and the overall gain of the band-reject filter below and above the notch frequency is expressed as V OUT /V IN =2A/(1+A). If you need additional rejection, cascade filter sections. Keep in mind that you might have to modify the circuit to account for out-of-band gain multiplication.EDN TAble 1 R Q Rejection at 60 Hz, and tHe filteR’s voltage gain as a function of tHe filteR Q Filter Q R Q (kΩ) Rejection (db) V OUT /V IN 0.75 1 40 1.33 1 2 35 1.5 1.25 3 30 1.6 2.5 8 25 1.8 5 18 20 1.9 10 38 15 1.95 Figure 1 This notch filter suppresses 60-Hz interference in low-frequency signals. 58 EDN | March 2013 [ www.edn.com ]
Analog designers form a unique blend of engineering discipline, creativity, individualism, passion, and out-of-the-box thinking. Planet Analog is your new playground and community. Explore: www.PlanetAnalog.com Blogs Message Boards Live Chats Whitepapers Educational Resources © 2013 UBM LLC
Page 1:
a vs. Si vs. GaN vs. SiC vs. Si vs.
Page 4 and 5:
The Trusted Leader for Any Measurem
Page 6 and 7:
Promoting the real benefits of auth
Page 8 and 9:
• CHiL ® Digital Control PowIRst
Page 10 and 11:
Register today to attend the larges
Page 12 and 13: edn.comment By Patrick Mannion, Bra
Page 14 and 15: pulse INNOVatIONS & INNOVatORS 10 9
Page 16 and 17: pulse Dash-cam video: benefit or di
Page 18 and 19: pulse Time-of-flight proximity sens
Page 20: pulse VOICES Peter Spitzer: Motivat
Page 23 and 24: Meet Your Dream Team Four great rea
Page 25 and 26: Introducing ... SR1 Audio Analyzer
Page 27 and 28: 2500-mAh Li-ion battery. The boost-
Page 29: T-1 LED Spacer mounts ® THiNK Keys
Page 32 and 33: Highly touted organic light-emittin
Page 34 and 35: Regulating cuRRent The LED-manufact
Page 36 and 37: ent sink of approximately 400 mV is
Page 38 and 39: a vs. Si vs. GaN vs. SiC vs. Si vs.
Page 40 and 41: EfficiEnt PowEr convErsion Efficien
Page 42 and 43: negligible charge storage permits t
Page 44 and 45: Cree Cree is in a unique position i
Page 46 and 47: Figure 7 In this chart showing semi
Page 48 and 49: By JacoB Beningo • Beningo engine
Page 50 and 51: version of code with a description
Page 52 and 53: V IN = 48V V OUT (V) 25 20 15 10 5
Page 54 and 55: Designing a power backup system is
Page 56 and 57: designideas ANALOG SIGNALS DIGITAL
Page 58 and 59: designideas VOLTAGE (V) ISO 1 ISO 2
Page 60 and 61: designideas 350 300 250 200 150 100
Page 64 and 65: supplychain Linking design and reso
Page 66 and 67: Make an IMPACT A whole new way of d
Page 68 and 69: DDS sweep generators Model 4007B an
Page 70 and 71: Tales from The Cube KenneTh Ciszews
Page 72: Charge BIG Batteries Fast I CHARGE
show all

201303.pdf 36567KB Mar 22 2013 09:11:22 PM

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?