Go Back   Home > Forums > >

Chip Amps Amplifiers based on integrated circuits

Op-amp input impedance when unpowered
Op-amp input impedance when unpowered
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
Old 11th June 2021, 06:42 AM   #21
jan.didden is offline jan.didden  Europe
diyAudio Member
jan.didden's Avatar
Join Date: May 2002
Location: Westende Resort, BE coast
If you separate the switches from the switching control, use DPDT small signal relays in R-2R, using one section for each stereo channel. That would be really compact, constant input Z, put the relay close to the signal circuitry and control from wherever you want.
That's what I used in the autoranger (OMRON relays G6K-2P-DC5) and it works extremely well.

  Reply With Quote
Old 11th June 2021, 09:08 AM   #22
newvirus2008 is offline newvirus2008  India
diyAudio Member
Join Date: Jun 2008
Yes, something using relays should be the ultimate switcher, very linear and all. Even with limited lifetimes and the unequal switching transitions of the LSB and MSB relays, they're likely to outlive most of the equipment in the signal chain.

Are you aware of any popular developments in the continuous domain? I happened to find a Thailand paper showing a simple opamp-only multiplier based on the identity (a+b)^2-(a-b)^2=4ab. Huge THDs though!
  Reply With Quote
Old 11th June 2021, 06:17 PM   #23
newvirus2008 is offline newvirus2008  India
diyAudio Member
Join Date: Jun 2008
I gather that there are only a few methods for proper multiplication in the continuous domain and none of these, in my opinion, seem to be worth the pain. It looks like I would do a modified R-2R ladder attenuator, if I have to do one someday. For now, I have settled for a fixed ratio.

Thank you all, especially Mr. Didden, for your valuable inputs and tips.
  Reply With Quote
Old 13th June 2021, 07:36 AM   #24
Mark Tillotson is offline Mark Tillotson
diyAudio Member
Join Date: May 2018
Location: Cambridge UK
Originally Posted by nigelwright7557 View Post
Not sure how wise it is to put volts on an op amp input with no power.
It could latch up and cause problems.
You'll probably damage/destroy the opamp front-end if you inject a strong signal when unpowered - this is one reason series resistors are often seen on inputs even though it increases noise - it helps protect the front-end pair.

Audio opamps usually have back-to-back diodes across the inputs to reduce the risk of zener-breakdown in the front-end (which knackers noise-performance permanently).

Opamps are remarkably robust when the inputs and outputs are within the supply rails - take them outside and all bets are
off - a good reason for protection schottkys to the rails.
  Reply to this post


Op-amp input impedance when unpoweredHide this!Advertise here!
Thread Tools

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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Unpowered full range OB laptop and phone speakers BasicHIFI1 Full Range 2 19th November 2020 03:07 AM
Yamaha RX-V373 and an unpowered sub mizino Subwoofers 3 29th November 2014 11:51 PM
Help with unpowered sub Randallm Subwoofers 7 22nd June 2011 08:06 PM
unpowered speakers frank12 Multi-Way 3 16th May 2005 05:12 AM
Input pot and input impedance Bricolo Parts 1 19th March 2003 01:59 PM

New To Site? Need Help?

All times are GMT. The time now is 11:21 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Copyright ©1999-2021 diyAudio