Hello everybody,
I'm currently designing a guitar amplifier around national semiconductor's LM4780 and I've I got a couple of questions from studying the datasheet (that thing is pretty long!).
I have built a couple of effects units and I'm currently in the process of designing a preamp for the unit that will handle all of the tone shaping so I'd like the output stage (LM4780) to be as clean as possible.
1. Is the bridge amplifier application circuit (page 5 of the datasheet) recommended? Is it reliable? I've at the application notes that heat can be a problem, could a fan-heatsink combo realistically overcome that limitation?
2. I seem to be a little confused regarding output power. I would have thought that starting from rail voltage Vcc and Vee and load impedance R_L I could calculate peak output power as
Ppeak=Vcc^2/R_load
and then divide by the square root of two to get rms power.
Some of the graphs at pages 10 and 11 just don't seem to add up to me...
3. At page 11 there are some graphs plotting Total Power Dissipation Vs Output Power/Channel. What exactly is Total Power Dissipation? Why does it go down a point? How can it be less than the Output Power at a high enough value (for R_L=8 Ohm, Output Power=60W, Total Power Dissipation=~55W)?
Hope someone can give me some answers!!!
thanks in advance
daniel
p.s. any info on how much power has been achieved by a single chip in bridge configuration?
I'm currently designing a guitar amplifier around national semiconductor's LM4780 and I've I got a couple of questions from studying the datasheet (that thing is pretty long!).
I have built a couple of effects units and I'm currently in the process of designing a preamp for the unit that will handle all of the tone shaping so I'd like the output stage (LM4780) to be as clean as possible.
1. Is the bridge amplifier application circuit (page 5 of the datasheet) recommended? Is it reliable? I've at the application notes that heat can be a problem, could a fan-heatsink combo realistically overcome that limitation?
2. I seem to be a little confused regarding output power. I would have thought that starting from rail voltage Vcc and Vee and load impedance R_L I could calculate peak output power as
Ppeak=Vcc^2/R_load
and then divide by the square root of two to get rms power.
Some of the graphs at pages 10 and 11 just don't seem to add up to me...
3. At page 11 there are some graphs plotting Total Power Dissipation Vs Output Power/Channel. What exactly is Total Power Dissipation? Why does it go down a point? How can it be less than the Output Power at a high enough value (for R_L=8 Ohm, Output Power=60W, Total Power Dissipation=~55W)?
Hope someone can give me some answers!!!
thanks in advance
daniel
p.s. any info on how much power has been achieved by a single chip in bridge configuration?