Siliconix & Siemens NMOS amplifiers

[steph_tsf]

Here is the Siliconix audio amplifier (published in October 1979, when VMOS hit the mass market).
Here is the Siemens BUZ20 application-note audio amplifier (published in 1982 maybe, when SIPMOS hit the mass market).

See attached files.

I guess audio freaks will love them, as they are non symetric, non complementary. If global feedback doesn't ruin everything, one can expect a smooth harmonic content with H2, H3, H4 and H5 showing in a nice undisturbed parabolic profile.

But, what about dV/dt ?
But, what about Class-B crossover distorsion ?
But, what about thermal stability ?

The Siliconix audio amplifier may not work, as F. de Dieuleveult (French Journalist) was known for making mistakes (distraction mainly) upon publishing articles. A proof of this is that the bias setting procedure he is describing, is completely nuts, referring to non-existing components. No doubt he re-numbered the components on the schematic, after he finished writing the article !

If somebody can provide a link to the genuine Siliconix application note entitled "DA76-1 - The VMOS Power FET Audio Amplifier", it would be fantastic.

What do you think about the Siemens BUZ20 application-note audio amplifier ?
I'm quite sure this worked, as it got published as a DIY mini-amplifier by the magazine Le Haut-Parleur (France and Belgium), authored by Etienne Lemery, who was (is still !) one of the best audio journalists here in France, always in serach for excellence.

Any comments, any suggestions welcome.

[wahab]

Originally Posted by steph_tsf

The Siliconix audio amplifier may not work, as F. de Dieuleveult (French Journalist) was known for making mistakes (distraction mainly) upon publishing articles. A proof of this is that the bias setting procedure he is describing, is completely nuts, referring to non-existing components. No doubt he re-numbered the components on the schematic, after he finished writing the article !

If my memory is good, Dieuleveult s amp was published in the french
review Radio Plans.
A refined schematic, as often with him despite some mistakes
as his 2 X 150W amp that did blow the output devices automatically.
Hey, he did use a single pair of 2N5631/2N6031 in his first try.
A month later ,he upgraded to four pairs..

He published in the same review a preamp using discrete op amps
that was truly wonderfull.

[steph_tsf]

The Spice simulation shows that the Siemens - Etienne Lemery amplifier delivers clean results with excellent bandwidth and slew-rate.

See attached .zip file. It is containing two Tina 7 Texas Instruments files ready to be simulated.

Tina 7 Texas Instruments is free and downloadable from SPICE-Based Analog Simulation Program - TINA-TI - TI Tool Folder

[apexaudio]

What do you think about the Siemens BUZ20 application-note audio amplifier ?
I'm quite sure this worked, as it got published as a DIY mini-amplifier by the magazine Le Haut-Parleur (France and Belgium), authored by Etienne Lemery, who was (is still !) one of the best audio journalists here in France, always in serach for excellence.

Any comments, any suggestions welcome.[/QUOTE]

I interested to see this DIY mini-amplifier, I made German Elektor BUZAMP long time ago, and yes he work.

[steph_tsf]

apexaudio,

it would have been appropriated to tell people that you started a thread about this particular Siemens BUZ20 NMOS amplifier one week after I started this one.

150W MOSFET Amplifier with IRFP250x2
Started on March 14th, 2010.

The simulation of this amplifier is here since long ! Why don't you asked me ?

Now that you encourage people to build this remarkable mis-estimated amp, why don't you explain in the exposition of your thread, that thermal runaway is going to happen unless you put a temperature sensor (thermistor symbol) in the definition of the 2nd differential pair current source ? Etienne Lemery showed a proper practical solution ages ago. Read the original schematic (provided above). There is no Vbe multiplier ! The quiescent current is defined by the voltage drops on the 1K resistors.

Once it is understood how the quiescent current gets defined, this amp doesn't deserve the bad reputation he got ages ago.

Be more careful next time when you "quote" me. Your previous message is confusing / misleading. You were in such a hurry ... so you see, that's quite transparent now ...

cheers and respectful,
Steph

(oops, with an attitude ?)

[apexaudio]

I am sorry Steph, I was made some simplier version in 80', and I share that. In a future, anything about this amp I will post on this thread.
Regards Mile

[steph_tsf]

Originally Posted by apexaudio

In a future, anything about this amp I will post on this thread. Regards Mile

Hello Mile, seems a good idea as the other thread has drifted, and is not concentrating anymore on the lovely simple Siemens BUZamp. I'm definitely sure there is a future for the Siemens BUZamp. Shall we design an add-on for getting a Class AB Soft Non-Switching Siemens BUZamp, following kenpeter research ?

[latala]

Their is a mistake in the right hand drawing the resistor is shown in the drain of the bottom buz20 instead of the source!
regards Trevor

[steph_tsf]

Originally Posted by latala

There is a mistake ... the resistor is shown in the drain of the bottom buz20 instead of the source.

What makes you saying this ? If you are basing on another Siemens BUZamp implementation, it would be nice to share the schematic.

[latala]

The function of the resistor is to assist in bias stability wth a v fet however if the resistor is in the drain it has no function !
regards Trevor