Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Solid State Talk all about solid state amplification.

Op Amp buffer/amplifier, quasi-complementary, need advice.
Op Amp buffer/amplifier, quasi-complementary, need advice.
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 25th September 2012, 11:41 AM   #11
jaycee is offline jaycee  United Kingdom
diyAudio Member
Join Date: Apr 2004
Location: Norwich, UK
The circuit you show isn't complete, but good enough to see whats going on.

The big problem with this arrangement is that there is gain in the output stage. This is difficult to stabilise and frequently causes oscillation. That is probably why you have had blown output transistors. There's also no emitter resistors so I expect the amp has gone into thermal runaway at times too.

I agree with the other posts here - if you are looking for a replacement amp to fit in a limited amount of PCB space, you should use a chip amp such as LM3886. You're not going to be able to build anything discrete that is as compact and reliable as those.
  Reply With Quote
Old 26th September 2012, 02:22 AM   #12
wponline is offline wponline  Philippines
diyAudio Member
Join Date: Nov 2007
Location: It's more fun in the Philippines
Originally Posted by jcx View Post
monolithic audio power amp chips - check the chip amp forum - LM3886, LM4780, TDA7293 are all pretty complete amps, have many project articles - sometimes known as "Gain Clones"

most have output protection, thermal overload protection circuits built in too
Hi guys,

To answer your earlier posts.

1. +/-12V supplies for op amp and DAC are from 7812 and 7912 regulators.
2. I've simplified the amplifier to include the op amp inputs. The DAC outputs a sinusoidal wave 0 to 10V/0 to -10V, direct coupled. For a 4 ohm load, the max current is 1.5A and through R60 is sensed from the output.
3. The damper circuit samples the output and when the voice coil stops, generates opposite and decaying wave. Fed back to + input of op amp. Capacitor coupled to prevent DC.
4. As for the output circuit with gain, I find similarity to LH0101.
5. Am I correct to say that the op amp just buffers the DAC output. The quasi-amplifier is just a voltage to current converter?
6. Is is possible to remove the quasi-amp gain and bring it outside the op amp + quasi-amp like the Walt Jung composite op amp + buffer? My problem is how to integrate the various resistors at the op amp inputs.
Attached Images
File Type: jpg Quasi buffer amp.JPG (85.1 KB, 79 views)
  Reply With Quote


Op Amp buffer/amplifier, quasi-complementary, need advice.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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
How to identify a quasi-complementary amplifier? motbuddy Solid State 53 30th August 2017 09:05 PM
2N3055 inside - commercial famous amplifier models, quasi complementary power output tiefbassuebertr Solid State 246 5th December 2016 05:12 PM
Quasi complementary outputs in a full complementary circuit xeclipse Solid State 12 11th January 2011 08:35 PM
Quasi complementary outputs in a full complementary circuit xeclipse Solid State 0 26th December 2010 08:08 PM
Quasi complementary headphone buffer ash_dac Headphone Systems 0 13th August 2006 12:35 PM

New To Site? Need Help?

All times are GMT. The time now is 04:08 PM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio