Hobby Electronics Basics LM1875 on a single supply

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Subject Author Date
LM1875 on a single supply mrdarrett 07-01-08
Posted by on July 1, 2008, 2:30 pm
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I was reading the datasheet for the LM1875
http://www.national.com/ds.cgi/LM/LM1875.pdf

and I noticed that they do have a schematic for a single supply (as
opposed to a +/- supply).

If running on a single supply, does the chip amplifer consume
significant power during quiet tracks?

Would this be pretty much the same as running the amplifier in Class A
mode (vs. Class AB)?

I'm trying to figure out if I really need a +/- power supply, or if I
can just go with a single supply (easier to build).

Thanks,

Michael

Posted by Don Bowey on July 1, 2008, 2:48 pm
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On 7/1/08 11:30 AM, in article
a1662fad-e0d7-4306-9e20-195abb1e7311@c19g2000prf.googlegroups.com,

> I was reading the datasheet for the LM1875
> http://www.national.com/ds.cgi/LM/LM1875.pdf
>
> and I noticed that they do have a schematic for a single supply (as
> opposed to a +/- supply).
>
> If running on a single supply, does the chip amplifer consume
> significant power during quiet tracks?
>
> Would this be pretty much the same as running the amplifier in Class A
> mode (vs. Class AB)?
>
> I'm trying to figure out if I really need a +/- power supply, or if I
> can just go with a single supply (easier to build).
>
> Thanks,
>
> Michael

The datasheet does have a "Typical Single Supply Operation" schematic.
Have another look.



Posted by on July 1, 2008, 2:55 pm
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> On 7/1/08 11:30 AM, in article
> a1662fad-e0d7-4306-9e20-195abb1e7...@c19g2000prf.googlegroups.com,
>
>
>
> > I was reading the datasheet for the LM1875
> >http://www.national.com/ds.cgi/LM/LM1875.pdf
>
> > and I noticed that they do have a schematic for a single supply (as
> > opposed to a +/- supply).
>
> > If running on a single supply, does the chip amplifer consume
> > significant power during quiet tracks?
>
> > Would this be pretty much the same as running the amplifier in Class A
> > mode (vs. Class AB)?
>
> > I'm trying to figure out if I really need a +/- power supply, or if I
> > can just go with a single supply (easier to build).
>
> > Thanks,
>
> > Michael
>
> The datasheet does have a "Typical Single Supply Operation" schematic.
> Have another look.


Yes, that's what I said. There is a schematic. It's on Page 2.
(amused grin)

Michael

Posted by John Fields on July 1, 2008, 3:15 pm
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On Tue, 1 Jul 2008 11:55:35 -0700 (PDT), mrdarrett@gmail.com wrote:

>> On 7/1/08 11:30 AM, in article
>> a1662fad-e0d7-4306-9e20-195abb1e7...@c19g2000prf.googlegroups.com,
>>
>>
>>
>> > I was reading the datasheet for the LM1875
>> >http://www.national.com/ds.cgi/LM/LM1875.pdf
>>
>> > and I noticed that they do have a schematic for a single supply (as
>> > opposed to a +/- supply).
>>
>> > If running on a single supply, does the chip amplifer consume
>> > significant power during quiet tracks?
>>
>> > Would this be pretty much the same as running the amplifier in Class A
>> > mode (vs. Class AB)?
>>
>> > I'm trying to figure out if I really need a +/- power supply, or if I
>> > can just go with a single supply (easier to build).
>>
>> > Thanks,
>>
>> > Michael
>>
>> The datasheet does have a "Typical Single Supply Operation" schematic.
>> Have another look.
>
>
>Yes, that's what I said. There is a schematic. It's on Page 2.
>(amused grin)

---
Look at "Supply Current" on page 2 and read: "Power Dissipation and
Heat Sinking" on page 6.

JF

Posted by on July 1, 2008, 4:30 pm
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> On Tue, 1 Jul 2008 11:55:35 -0700 (PDT), mrdarr...@gmail.com wrote:
> >> On 7/1/08 11:30 AM, in article
> >> a1662fad-e0d7-4306-9e20-195abb1e7...@c19g2000prf.googlegroups.com,
>
> >> > I was reading the datasheet for the LM1875
> >> >http://www.national.com/ds.cgi/LM/LM1875.pdf
>
> >> > and I noticed that they do have a schematic for a single supply (as
> >> > opposed to a +/- supply).
>
> >> > If running on a single supply, does the chip amplifer consume
> >> > significant power during quiet tracks?
>
> >> > Would this be pretty much the same as running the amplifier in Class A
> >> > mode (vs. Class AB)?
>
> >> > I'm trying to figure out if I really need a +/- power supply, or if I
> >> > can just go with a single supply (easier to build).
>
> >> > Thanks,
>
> >> > Michael
>
> >> The datasheet does have a "Typical Single Supply Operation" schematic.
> >> Have another look.
>
> >Yes, that's what I said. There is a schematic. It's on Page 2.
> >(amused grin)
>
> ---
> Look at "Supply Current" on page 2 and read: "Power Dissipation and
> Heat Sinking" on page 6.
>
> JF



Ah, so apparently the chip does not use more power with a single
supply than with a +/- supply.

Is there any reason why I should NOT use a single supply with this
chip?

Thanks,

Michael

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