Transconductance Amplifier. - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

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
Reply
 
Thread Tools Search this Thread
Old 6th March 2015, 02:56 PM   #1
dady is offline dady  Argentina
diyAudio Member
 
dady's Avatar
 
Join Date: Oct 2002
Location: Punta Prima, Menorca, Spain
Send a message via MSN to dady Send a message via Skype™ to dady
Default Transconductance Amplifier.

In honour of the true. Which are they, How can I recognize one of them.
I coming watching with all my mind and trying to think how they work and which is the clue part in the circuit. I read the most articles I could not got but at the moment is no objective for my mind. The F1 the F2, the CSX, the A75. Please if anybody in this honourable forum, maybe there are somebody like me. Some body said that high sensitive fullrange horns are the perfect weeding for they. I have one since long time and now I am a little tired with it. I read the article "Current Source Amplifiers and sensitive full range drivers" And others from Joe Rasmusen. But I can't recognize.
Thanks in advance
__________________
Esteban Bikic

Last edited by dady; 6th March 2015 at 04:05 PM.
  Reply With Quote
Old 6th March 2015, 03:15 PM   #2
diyAudio Member
 
Join Date: May 2011
Location: Silicon Valley
Pragmatically speaking you can use open loop output impedance as an indicator. If output impedance Zout exceeds (10 * Vsupply / Isupply_max) then the amplifier being studied is probably a transconductance amplifier.

Let's work an example. The Texas Instruments LM13700 IC is, unambiguously and indisputably, a transconductance amplifier. See below. According to the datasheet its Vsupply is 36V and its Isupply_max is 20mA. Thus our pragmatic indicator would say "yes it is a transconductance amplifier" if and only if
  • Zout > (10 * 36 / 0.02) ... ... ... numerically, Zout > 18 kohms
The datasheet says that Zout for the LM13700 exceeds 10 megohms. So this indicator says, "yes the LM13700 IC certainly is a transconductance amplifier".

Other members may have their own preferred value of the coefficient in the inequality; they may wish to replace "10" by a different number.

_
Attached Images
File Type: png Transconductance_Amplifier.png (45.5 KB, 187 views)
  Reply With Quote
Old 6th March 2015, 07:55 PM   #3
OllBoll is offline OllBoll  Sweden
diyAudio Member
 
Join Date: Nov 2010
Voltage source amplifier => low output impedance relative to speaker.
Current source amplifier => high output impedance relative to speaker.

Also, it is a good idea to avoid using current source amps within ~ 2 octaves of driver fs. They really shine on multi way speakers though.

( I have Zen-ish current source amps with ~ 700 output impedance for my mid / tweets )
  Reply With Quote
Old 6th March 2015, 08:10 PM   #4
diyAudio Member
 
Join Date: Sep 2004
Location: Göteborg
Quote:
Also, it is a good idea to avoid using current source amps within ~ 2 octaves of driver fs
This depends on the Qms and the enclosure the driver is in.

My BIBs with B&C 10PS26 work very good with +500 ohm output impedance.
The very wide band hornloading starting a full octave below fs, and keeps the cone well controlled at Fs even though a Qms of the driver of 2,9.

regards,
Johannes
__________________
We live in a horizontal world, why use vertical topologies???
  Reply With Quote
Old 6th March 2015, 08:10 PM   #5
dady is offline dady  Argentina
diyAudio Member
 
dady's Avatar
 
Join Date: Oct 2002
Location: Punta Prima, Menorca, Spain
Send a message via MSN to dady Send a message via Skype™ to dady

Hi, thanks gentlemen, BTW that is true, operational transconductance amplifier and the idea of voltage/current-source amplifier with the correlative low and high impedance over the speaker.
Thanks a lot but I wanna recognize a topology that show us. People say that F2J, the only I can distinguish over other is the parallel of resistors with the load. But essentially how they work?
The paradigm of damping, load and bandwidth in amplifiers is clear, I guess until now. Somebody, talked about high impedance over the speaker. That give an unbalance between the out with the load. I knew that triode amps became more linear with higher impedance of load.
Best Regards
__________________
Esteban Bikic
  Reply With Quote

Reply


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
help with transconductance amplifier dataplex Chip Amps 3 6th March 2014 01:02 AM
A transconductance tube amplifier Nikolas Ojala Tubes / Valves 2 8th August 2013 12:01 AM
LM3886 as transconductance amplifier? squadra Chip Amps 4 23rd April 2008 10:16 PM
A Transconductance Amplifier Duo Solid State 27 19th February 2007 07:59 PM
A SOZ Transconductance Amplifier gl Pass Labs 21 16th December 2005 07:42 PM


New To Site? Need Help?

All times are GMT. The time now is 01:06 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2015 DragonByte Technologies Ltd.
Copyright ©1999-2015 diyAudio

Content Relevant URLs by vBSEO 3.3.2