questions on Class B audio amplifier

[[email protected]]

"John Fields"



** 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

Gain problem could be fixed with two Sziklai pairs of transistors,
right?

Michael

 

[[email protected]]

Pure class B will have some crossover distortion, because the opamps
can't slew through the deadband infinitely fast.

Replacing the right-most 0.22 uF cap with a resistor *can* kill the
crossover distortion.




Yes, but uses a lot more parts. Some people like that.

John

For those who want to impress with More Parts... this Class D chip amp
is for you... page 12 : http://www.zetex.com/3.0/pdf/zxcd1000.pdf

Michael

 

[Phil Allison]

"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,

** Err - not true.

The output current is limited by the Hfe of the TIP41/42s to about 700 - 800
mA peak, since the TL082 has internal limiting at about +/-15mA.

hence will blow up pretty much as soon as wiring it up to a speaker is
attempted

** Not true at all.



...... Phil

 

[Kevin Aylward]

"Kevin Aylward"


** Err - not true.

Ok... the gain aint infinite...whatever....

Kevin Aylward
www.kevinaylward.co.uk
www.blonddee.co.uk
www.anasoft.co.uk - SuperSpice