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BA5406 schematic typo?

Started by Bitrex April 4, 2011
I'm looking at the equivalent schematic for the BA5406 IC power amp here 
on page 2:

http://www.kitsrus.com/projects/ba5406.pdf

Pin 3 is a boostrap input, I believe to increase the compliance of the 
current mirror loads and therefore the positive going saturation voltage 
of the upper Darlington pair, by connecting it via a capacitor to the 
output.  But I don't think it's really internally connected to 
Vcc...Connecting the output through a capacitor to Vcc would be kind of 
dumb, right?
On Mon, 04 Apr 2011 17:59:10 -0400, Bitrex <bitrex@de.lete.earthlink.net> wrote:

>I'm looking at the equivalent schematic for the BA5406 IC power amp here >on page 2: > >http://www.kitsrus.com/projects/ba5406.pdf > >Pin 3 is a boostrap input, I believe to increase the compliance of the >current mirror loads and therefore the positive going saturation voltage >of the upper Darlington pair, by connecting it via a capacitor to the >output. But I don't think it's really internally connected to >Vcc...Connecting the output through a capacitor to Vcc would be kind of >dumb, right?
Yeah, too dumb. Someone dropped extra blob there by accident. You can tell by viewing similar devices from others, perhaps same manuf? Grant.
On 4/4/2011 9:49 PM, Grant wrote:
> On Mon, 04 Apr 2011 17:59:10 -0400, Bitrex<bitrex@de.lete.earthlink.net> wrote: > >> I'm looking at the equivalent schematic for the BA5406 IC power amp here >> on page 2: >> >> http://www.kitsrus.com/projects/ba5406.pdf >> >> Pin 3 is a boostrap input, I believe to increase the compliance of the >> current mirror loads and therefore the positive going saturation voltage >> of the upper Darlington pair, by connecting it via a capacitor to the >> output. But I don't think it's really internally connected to >> Vcc...Connecting the output through a capacitor to Vcc would be kind of >> dumb, right? > > Yeah, too dumb. > > Someone dropped extra blob there by accident. You can tell by viewing > similar devices from others, perhaps same manuf? > > Grant.
Thanks for the confirmation of what I suspected. I had to puzzle a bit over how the supposedly class AB output stage on this circuit worked; I came to the realization that it could only work in an IC where the bias -setting diodes are diode connected transistors, with everything basically matched and you know what the differences in Vbe are going to be for different diode/transistor currents. In that way I guess they're able to get a class AB output without using the traditional method of a Vbe multiplier and emitter resistors on the output transistors. The bootstrap circuit is a pretty clever way of increasing the available output power at low voltages.
http://circuitschematicelectronics.blogspot.de/2012/04/ba5406-10w-stereo-power-amplifier.html#.U6sAY_l_sZl :D
On Wed, 25 Jun 2014 10:06:23 -0700 (PDT), linus.bantel@googlemail.com
wrote:

>http://circuitschematicelectronics.blogspot.de/2012/04/ba5406-10w-stereo-power-amplifier.html#.U6sAY_l_sZl :D
Audio people love to use potentiometers backwards. They do a lot of other stupid stuff, too. I think that, once people put in the effort to build their own audio amps, they like the sound, no matter how bad it actually is. -- John Larkin Highland Technology, Inc jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On 25/06/2014 18:06, linus.bantel@googlemail.com wrote:
> http://circuitschematicelectronics.blogspot.de/2012/04/ba5406-10w-stereo-power-amplifier.html#.U6sAY_l_sZl :D >
That must have been English -> Some Other Language -> English which would explain 'left' = 'not here'. Although I suspect Jim T (and most US contributors) would associate 'left' with 'not here'. Cheers -- Syd
On Wed, 25 Jun 2014 10:06:23 -0700 (PDT), linus.bantel@googlemail.com
wrote:

>http://circuitschematicelectronics.blogspot.de/2012/04/ba5406-10w-stereo-power-amplifier.html#.U6sAY_l_sZl :D
It's just current summing. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.