questions on Class B audio amplifier

[[email protected]]

I took a look at this:
http://openbookproject.net//electricCircuits/Exper/EXP_6.html#xtocid24829

It appears that this unit's max continuous power output on +/-12VDC at
4 ohms is 18W, if I calculated that right...

I wanted to build it, but I realized that increasing the voltage much
beyond +/- 12V would exceed the TL082 op amp's maximum voltage spec.

If I used a couple of higher-voltage TLE2141Cs, good to +/- 22V, would
this give a max continuous output power of 60W?

Since this is class B, and not Class AB... does the first op amp in
the schematic above do a good job of removing the "dead time" between
crossover? THD < 1%?

Does this Class B amp waste less power than Class AB (since only one
transistor is on at a time)?

I'm guessing that all the "junk" (input stage, VAS) between the line
input and output transistors on a typical power amplifier schematic
serves pretty much the same purpose of the two op amps here...?

Thanks,

Michael

 

[Jamie]

I took a look at this:
http://openbookproject.net//electricCircuits/Exper/EXP_6.html#xtocid24829

It appears that this unit's max continuous power output on +/-12VDC at
4 ohms is 18W, if I calculated that right...

I wanted to build it, but I realized that increasing the voltage much
beyond +/- 12V would exceed the TL082 op amp's maximum voltage spec.

If I used a couple of higher-voltage TLE2141Cs, good to +/- 22V, would
this give a max continuous output power of 60W?

Since this is class B, and not Class AB... does the first op amp in
the schematic above do a good job of removing the "dead time" between
crossover? THD < 1%?

Does this Class B amp waste less power than Class AB (since only one
transistor is on at a time)?

I'm guessing that all the "junk" (input stage, VAS) between the line
input and output transistors on a typical power amplifier schematic
serves pretty much the same purpose of the two op amps here...?

Thanks,

Michael

Look at using a LM1875 Ic amp, that chip starts at 16 Vcc up to 60 Vcc.

if you drive it with a complementary supply, then it's 8..30 Vcc/Vee
etc..
This chip does 20 Watts and can source/sink 4 Amps.
that's enough to drive some heavy complementary trannies.


http://webpages.charter.net/jamie_5"

 

[Eeyore]

I took a look at this:
http://openbookproject.net//electricCircuits/Exper/EXP_6.html#xtocid24829

It appears that this unit's max continuous power output on +/-12VDC at
4 ohms is 18W, if I calculated that right...

I wanted to build it, but I realized that increasing the voltage much
beyond +/- 12V would exceed the TL082 op amp's maximum voltage spec.

Why do you waste your time like this ?

Please become an adult.

Graham

 

[Phil Allison]

I took a look at this:
http://openbookproject.net//electricCircuits/Exper/EXP_6.html#xtocid24829

It appears that this unit's max continuous power output on +/-12VDC at
4 ohms is 18W, if I calculated that right...

** Nope - it is actually much less.

I wanted to build it, but I realized that increasing the voltage much
beyond +/- 12V would exceed the TL082 op amp's maximum voltage spec.

If I used a couple of higher-voltage TLE2141Cs, good to +/- 22V, would
this give a max continuous output power of 60W?

** Not a snowflake's chance in hell.

Since this is class B, and not Class AB... does the first op amp in
the schematic above do a good job of removing the "dead time" between
crossover? THD < 1%?

** No to both.

Does this Class B amp waste less power than Class AB (since only one
transistor is on at a time)?

** Not when delivering any power into a load.

I'm guessing that all the "junk" (input stage, VAS) between the line
input and output transistors on a typical power amplifier schematic
serves pretty much the same purpose of the two op amps here...?

** It is a complementary BJT follower /current booster tacked onto the
output of an op-amp.

Good of a couple of watts of lo-fi.

You are UTTERLY clueless.



...... Phil

 

[Eeyore]

I took a look at this:
http://openbookproject.net//electricCircuits/Exper/EXP_6.html#xtocid24829

It appears that this unit's max continuous power output on +/-12VDC at
4 ohms is 18W, if I calculated that right...

I wanted to build it, but I realized that increasing the voltage much
beyond +/- 12V would exceed the TL082 op amp's maximum voltage spec.

If I used a couple of higher-voltage TLE2141Cs, good to +/- 22V, would
this give a max continuous output power of 60W?

Since this is class B, and not Class AB... does the first op amp in
the schematic above do a good job of removing the "dead time" between
crossover? THD < 1%?

Does this Class B amp waste less power than Class AB (since only one
transistor is on at a time)?

Yes but it sounds shit.

Graham

 

[Eeyore]

---
Same old shit, eh, Graham?

The guy is obviously having some difficulty wrapping his head around a
problem and isn't afraid to admit it, and instead of giving him a
helping hand, you give him a slap.

What a really mean bastard you are.

Nothing compared to you.

 

[Eeyore]

Look at using a LM1875 Ic amp, that chip starts at 16 Vcc up to 60 Vcc.

if you drive it with a complementary supply, then it's 8..30 Vcc/Vee
etc..
This chip does 20 Watts and can source/sink 4 Amps.
that's enough to drive some heavy complementary trannies.

Pure Jamie bollocks as ever.

 

[Eeyore]

Yes, but a typical power amp sounds better....

And Universities are turning out kids even stupider than this !

Graham

 

[Phil Allison]

"John Fields"

---
You calculated it right, but the TL082 isn't a rail-to-rail output
opamp, so the output into the emitter follower pair would be
considerably less than 12V resulting in, consequently, less than 18
watts CW into the four ohm load.
---

** Lets see what it *really* is then:

From the data on the TL082, with +/-12 volt rails and say 500 ohms load, the
available output swing is +/- 7 volts.

Equates to 14mA peak.

From the data on the TIP41, Hfe = 50typ at Ic=1A & Vce= 4 volts.

50 times 15 = 700mA.

700 mA into 4 ohms = 2.8 volts peak.

Or 1 watt, rms continuos.

Long, long way from 18 .........




....... Phil

 

[[email protected]]

"John Fields"



** Lets see what it *really* is then:

Ah, numbers... goodie...

From the data on the TL082, with +/-12 volt rails and say 500 ohms load, the
available output swing is +/- 7 volts.

Where did you get 500 ohms for load?

Equates to 14mA peak.

From the data on the TIP41, Hfe = 50typ at Ic=1A & Vce= 4 volts.

50 times 15 = 700mA.

700 mA into 4 ohms = 2.8 volts peak.

Or 1 watt, rms continuos.

Long, long way from 18 .........

Yep...


...... Phil

Thanks,

Michael

 

[Phil Allison]

Where did you get 500 ohms for load?

** See above.

 

[Eeyore]

---
So, you admit you've met your master?

For years now, in an effort to try to communicate honestly, I've tried
being kind to you, and cordial, and courteous, and objective, and
logical, and even friendly, but it seems that's all come to naught since
all you're interested in is denigrating anyone who brushes up against
your holy space and questions your opinions.

You just described yourself beautitfully.

Graham

 

[Eeyore]

Ah, numbers... goodie...


Where did you get 500 ohms for load?

Rl * hFE is a good first stab.

For God's sake get yourself a good book on electronics and stop buggering about
with websites written by intellectual cripples. I hear The Art of Electronics is
very good.

Graham

 

[Eeyore]

I took a look at this:
http://openbookproject.net//electricCircuits/Exper/EXP_6.html#xtocid24829

It's a total heap of garbage. It's almost beyond a joke. If the rest of the
site is like that then try to forget anything you 'learnt' there.

Graham

 

[Phil Allison]

"John Fields"

Eeyore>

** Try:

http://www.grahamstevenson.co.uk/

Was available up until a few days ago.

But since the pommy puke has been issuing all kinda legalistic sounding
threats against ALL his imaginary on line enemies - the gutless pommy
poonce musta pulled it.

Besides revealing his residential address - it had nothing whatever to
say.

Just like the man himself.




...... Phil

 

[Kevin Aylward]

For starters, the pot can be set to infinite gain, making the amp output go
to the rail and take out the speaker due to amp offsets. There is no current
limiting, hence will blow up pretty much as soon as wiring it up to a
speaker is attempted.

The schematic is truly a non starter.

Kevin Aylward

www.kevinaylward.co.uk

 

[Kevin Aylward]

And Universities are turning out kids even stupider than this !

Graham

Shirley you mean knowledge challenged?

Kevin Aylward

www.kevinaylward.co.uk

 

[BobG]

Seems like you could get rid of the 1st amp... it just buffers the 10k
pot. You could make the 2nd amp non inverting and feed the input pot
wiper into the + input.

 

[Rich Grise]

Would you two please take your personal piss-fest elsewhere? This is
sci.electronics.basics, where there is no such thing as a dumb quetion;
all newbies are welcome here. Remember, we were all beginners once.

Thanks,
Rich

 

[Rich Grise]

Shirley you mean knowledge challenged?

Well, stupid is as stupid does. ;-)

Cheers!
Rich