Yet another complementary amp - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Solid State Talk all about solid state amplification.

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 24th October 2002, 04:22 PM   #1
diyAudio Member
Join Date: May 2002
Location: Switzerland
Default Yet another complementary amp

I was playing around with P-SPICE a little and came to the circuit posted below.

I first wanted a fully complementary TWO-stage amplifier with MOSFET output stages and the results didn't look that bad but not too promising either.
One of the requirements were that the output devices have to be operating in common source.

So I went further and came to the "final" circuit after some additions.

The whole cicuit is inverting and has four inner feedback loops (2 x 2 to be exact) and one overall feedback loop. The feedback network might have to be rearranged in practice (i.e. so that smaller resistor values can be used) because it might be difficult to use that small a capacitor (C5) because the circuit's parasitic capacitances may be much higher than that.

There is a restriction to a maximum of 10 transistors with my trial version. That's why I used DC voltage sources instead of transistors, zeners etc for bias stabilising, DC-offset correction etc.
I also wanted to use cascodes instead of just Q7 and Q8 but with the aforementioned restriction .........
Also the devices used are not the most sexy ones, but I am always too lazy when it comes to import models .......

What I specially like is the driver/output stage topology. It have first seen this in the German magazine Elrad about 20 years ago used within a 300 watt BJT amp. I think this design was originally published in an Australian magazine before, but I'm not sure. With this topology driver tansistors with lower Uce rating can be used which are more easily obtained and sometimes have higher fT and higher beta.

The output devices have to be biased quite high (around 200 mA) to obtain good performance.
I know that simulations and "the real world" will never be the same. But the figures I got looked promising anyway:

THD figures were almost the same for 1 kHz and 20 kHz and are mainly consisting of k2 and k3.
For an output voltage-swing of +- 10 Volts (i.e. 20 Vpp) k2 was 0.005 % and k3 was 0.002 %.
For +- 1 Volt k2 was 0.001 % and k3 was 0.0005 %.
Frequency response reached from DC to > 800 kHz.


Attached Files
File Type: zip (10.0 KB, 413 views)
  Reply With Quote
Old 10th May 2011, 08:01 PM   #2
diyAudio Member
Workhorse's Avatar
Join Date: Dec 2004
Strangely no one replied to this thread which was buried under the siege of time.

Hello Charles,

The Frontend is unique, if i am correct then the 47k resistors from VAS collectors to CB emitters are acting as feedback resistors.

  Reply With Quote
Old 11th May 2011, 05:43 AM   #3
CBS240 is offline CBS240  United States
diyAudio Member
CBS240's Avatar
Join Date: Aug 2005
Location: K-town
Hi Kanwar

It is a bit different, a diamond buffer driven CFP. I bet it would make a good pre-amp circuit. I wonder if the CFP stage with it's local feedback, could not provide enough voltage gain to drive the driver/outputs as followers. Source follower is more stable and easier on the driver stage wrt Cin, IMO. But then you would have to increase the front end VAS supply voltage to account for loss of Vgs....or use laterals.
All the trouble I've ever been in started out as fun......
  Reply With Quote
Old 11th May 2011, 07:30 AM   #4
diyAudio Member
Workhorse's Avatar
Join Date: Dec 2004


A pre-amp with pure class-A bias using this topology would certainly give better results.

The local feedback arrangement in VAS looks interesting though.
  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
Complementary V-FET's other than IRF's??? Ultima Thule Parts 36 30th June 2014 07:03 PM
Complementary vs NPN / NPN toptip Solid State 1 11th February 2008 03:31 PM
complementary zen v5 input Z? nobody special Pass Labs 5 19th May 2006 06:00 PM
Complementary med pwr transistors? jan.didden Parts 22 16th June 2004 08:18 AM
Zen v5 non-complementary Stefano Pass Labs 15 10th August 2003 05:09 PM

New To Site? Need Help?

All times are GMT. The time now is 05:44 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