input impedance of active filters.q - diyAudio
Go Back   Home > Forums > Source & Line > Analogue Source
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 16th June 2003, 04:27 AM   #1
diyAudio Member
Join Date: Dec 2001
Location: SIUE, Illinois, USA
Default input impedance of active filters.q

i was looking around at the demo of "filter solutions" and noticed each circut type has a "Zin" which has a phase, magnitude, and group-delay. so how does this affect the phase, magnitude, and group-delay of the filter?
if only it could be used for good, not evil...
  Reply With Quote
Old 25th June 2003, 11:07 PM   #2
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
EC8010's Avatar
Join Date: Jan 2003
Location: Near London. UK
Active filters are usually Sallen & Key designs. They work by applying positive feedback, and their input impedance is often a lot lower than casual inspection would suggest. They need to be fed from a low impedance source. In op-amp terms, that means a buffer, in transistor terms, an emitter follower, and valves need a cathode follower. Buffers should not be shared.

Failure to buffer properly is likely to cause frequency response errors and distortion in the preceding stage. That's the effect of their input impedance...
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
  Reply With Quote


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Active notch filters neutron7 Full Range 2 19th November 2006 11:51 AM
Bob Pease on Active Filters Speedskater Solid State 0 6th October 2006 10:24 PM
preamp active filters DD_Davo Solid State 29 7th April 2006 01:23 AM
active filters: which resistors to buy akunec Chip Amps 11 13th March 2005 01:09 PM
Which op amps do you use for active filters?? zx3chris Parts 4 25th April 2003 06:42 AM

New To Site? Need Help?

All times are GMT. The time now is 01:27 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2