questions on Class B audio amplifier

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]

mrdarrett@gmail.com wrote:

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]

mrdarrett@gmail.com wrote:

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]

<mrdarrett@gmail.com>

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

 

[John Fields]

On Wed, 22 Oct 2008 01:09:17 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

mrdarrett@gmail.com wrote:

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.

---
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.

JF

 

[Tim Wescott]

mrdarrett@gmail.com wrote:

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...

Always show your assumptions.

You're assuming you can get 24V p-p out of that circuit -- review the
base-emitter drop of a transistor, and the voltage drop of the op-amp
before you make any promises.

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?

See my comment above. Yes, but (but this is not the way to achieve that!!!)

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%?

Read the web page. If you have an oscilloscope to measure output -- try
it. If you don't, try it out on LTSpice (which is free). Use their
"generic 1-pole op-amp" with a GBW to equal the TL082, and try it at
different frequencies.

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

In theory, yes, in practice -- what's your operating point? What class
AB amp are you comparing it to? What frequency signal are you pumping
through?

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...?

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

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

 

[Eeyore]

mrdarrett@gmail.com wrote:

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]

John Fields wrote:

On Wed, 22 Oct 2008 01:09:17 +0100, Eeyore
rabbitsfriendsandrelations@hotmail.com> wrote:



mrdarrett@gmail.com wrote:

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.

---
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]

Jamie wrote:

mrdarrett@gmail.com wrote:

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.

Pure Jamie bollocks as ever.

 

[Eeyore]

Tim Wescott wrote:

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

And Universities are turning out kids even stupider than this !

Graham

 

[John Fields]

On Tue, 21 Oct 2008 16:13:57 -0700 (PDT), mrdarrett@gmail.com wrote:

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...

---
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.
---

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.

---
That's not true.

Here's the data sheet for the TL085:

http://focus.ti.com/lit/ds/symlink/tl082.pdf
---

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

---
Well, first you'd have to get your supply up to +/- whatever was needed
to get 22V into the load by considering all the losses and voltage drops
incurred along the path from input to output, and then you'd have to
make sure that everything in the loop was happy with its supply.

The magic word is "headroom"
---

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%?

---
The first opamp has nothing to do with reducing crossover distortion.
Go back and read the article again.
---

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

---
A tiny bit less, if the bias is right, since both transistors in an AB
stage would be on simultaneously while the load was being transferred
from the source to the sink and Vice Versa.
---

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...?

---
???

JF

 

[Phil Allison]

"John Fields"

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...

---
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

 

[John Fields]

On Wed, 22 Oct 2008 02:35:37 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

John Fields wrote:

On Wed, 22 Oct 2008 01:09:17 +0100, Eeyore
rabbitsfriendsandrelations@hotmail.com> wrote:



mrdarrett@gmail.com wrote:

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.

---
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.

---
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.

JF

 

[John Fields]

On Wed, 22 Oct 2008 13:49:28 +1100, "Phil Allison"
<philallison@tpg.com.au> wrote:

"John Fields"

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...

---
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.

---
RMS?

JF

 

[Eeyore]

John Fields wrote:

On Wed, 22 Oct 2008 02:35:37 +0100, Eeyore
rabbitsfriendsandrelations@hotmail.com> wrote:



John Fields wrote:

On Wed, 22 Oct 2008 01:09:17 +0100, Eeyore
rabbitsfriendsandrelations@hotmail.com> wrote:



mrdarrett@gmail.com wrote:

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.

---
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.

---
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]

mrdarrett@gmail.com wrote:

"Phil Allison" <philalli...@tpg.com.au> wrote:
"John Fields"

I took a look at this:

http://openbookproject.net//electricCircuits/Exper/EXP_6.html#xtocid2...

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

---
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:

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?

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]

mrdarrett@gmail.com wrote:

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

 

On Oct 21, 7:49 pm, "Phil Allison" <philalli...@tpg.com.au> wrote:

"John Fields"

I took a look at this:

http://openbookproject.net//electricCircuits/Exper/EXP_6.html#xtocid2...

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

---
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:

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

 

[John Fields]

On Wed, 22 Oct 2008 07:55:01 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

John Fields wrote:

On Wed, 22 Oct 2008 02:35:37 +0100, Eeyore
rabbitsfriendsandrelations@hotmail.com> wrote:



John Fields wrote:

On Wed, 22 Oct 2008 01:09:17 +0100, Eeyore
rabbitsfriendsandrelations@hotmail.com> wrote:



mrdarrett@gmail.com wrote:

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.

---
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.

---
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.

---
Why, thank you Graham!

And how do you think I described you?

Beau_tit_fully as well?

Freudian slip: When you say one thing but mean your mother.


JF

 

[John Fields]

On Wed, 22 Oct 2008 07:58:42 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

mrdarrett@gmail.com wrote:

"Phil Allison" <philalli...@tpg.com.au> wrote:
"John Fields"

I took a look at this:

http://openbookproject.net//electricCircuits/Exper/EXP_6.html#xtocid2...

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

---
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:

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?

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.

---
You have a web site?
---

I hear The Art of Electronics is very good.

---
There'd be nothing wrong with this newsgroup, either, if it weren't for
nasty little bitches like you spewing vitriol every chance they got.

JF