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National Semiconductor introduced the LME49810 integrated circuit in May 2007. There was an official news release made on 23rd July 2007.
The LME49810 consists of a differential-input high-gain operational-amplifier, but there are several features which set it apart from most single op-amps. The LME49810 has a remarkable output swing of up to 190 Volts peak-to-peak, and the output is split into two separate halves, a 'source' and a 'sink'. This makes it ideal for driving the output stage of an audio power amplifier and in excess of 500 Watts RMS can be delivered into an 8 Ohm load.
There are two bias pins for connecting a Vbe multiplier for temperature compensation of the output stage quiescent conditions. The Baker Clamp feature provides soft clipping when the amplifier is overdriven by preventing the driver transistors from saturating. This reduces unwanted artefacts at high peak output power levels. A 'clip flag' pin allows the clipping condition to be indicated by a LED.
The 'source' and 'sink' outputs can pass up to 50 milliAmps of current. Depending on the output power, the output transistors (BJTs) may not need to be preceded by driver transistors. It is also possible to adapt the LME49810 to drive a variety of power semiconductor devices such as directly driving MOSFETs, or even thermionic valves (tubes). The outputs have a maximum permitted differential of 10 Volts.
Have you read something like this before? Maybe you are thinking of the LM4702 dual driver op-amp, for which I have my own web page.
In recent years the popularity of "chip amp" or "gainclone" audio power amplifiers
has centred around the simplicity of using modern amplifier chips which have the power
output stages integrated on to the chip. An advantage of the LME49810 is that
output stage can be whatever the designer cares to use. This is discussed further on
the LM4702 page.
The Total Harmonic Distortion plus Noise (THD+N) characteristic of the LME49810 is very good.
At 30 Volts RMS output of a 1 KHz sine wave, THD+N is about 0.0007% across a 20 Hz to 30 KHz bandwidth.
Some other important specifications of the LME49810 are: Slew rate is 50 V/uS. Open loop voltage gain is 120 dB at DC.
Power Supply Rejection Ratio (PSRR) is 110 dB. There is also a 'mute' function which can be used to start up or shut down the
amplifier. It has automatic thermal shut-down at 150 °C but no other overload protection circuitry.
The Data Sheet (PDF, size 867K, 22 pages) is
available in the LME49810 product folder.
It contains a schematic for a typical application (JPEG image, size 31K)
and the PCB layout of the evaluation board. Information is also provided on
the mute function, thermal protection, power dissipation, heat sinking, selection of external components
and tips on avoiding thermal run-away when using bipolar output stages.
The part is available in one grade, which is a customised TO-247 package. It is in full production as at 1 June 2007. The approximate unit prices is
not available as at 1 June 2007.
The LME49810 generated some interest on the
Chip Amps forum
of DiyAudio.com, commencing in a
LM4702 discussion thread on 31st May 2007.
I started a LME49810 discussion thread on 4th June 2007.
The concept of a high output swing op-amp for driving an audio power output stage is not new,
and this is discussed further on the LM4702 page.
This page refers to the following links:
Performance
Product Data
Practical Experiences
Previous Generation Drivers
Pin Connections
© National Semiconductor Corporation 2007.
Reproduced and annotated for the purpose of fair research from the LME49810 PDF data sheet dated May 2007.
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© Glenn Baddeley 2007.
http://home.pacific.net.au/~gnb/audio/lme49810.html was last updated 24 July 2007.
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