TPA6120A2 Question

[odigg]

Hi,

I'm looking at the spec of this chip and it states that it can pump out 1.5W into 32 ohms, or 80mw into 600 ohms.

In contrast, the CK2III specs state it can 1.4W into 33 ohms and 0.15W into 330 ohms.

So is the TPA6120A2 capable of providing more power output than the CK2III? I know this seems like a very basic question, but I don't know if there is more to the TPA6120A2 spec than meet the eye. Perhaps the power output is theoretical and the practical output will be less?

As you can guess, I don't know all that much about audio amplifiers.

 

[jcx]

as always in engineering the answer is "it depends"

in this case on power supply V and heatsink capacity

the TPA6120 can put out 400 mA

1/2 *.4^2 * 32 = 2.5 Wrms into 32 Ohm load (with > +/-14 V supply)

the limit is removing heat from the chip, with 2 channels at full power and ~ 70% efficency for linear Class AB you need to keep the chip cool while removing ~1.5-2 Watts of heat - this is doable if you follow the datasheet recommended layout and use solder paste and reflow to connect the PwrPad to a large enough power plane - not as easy for the typical hobbyist but there are hacks that work for hand soldering and getting the heat removal - or a dedicated 32 Ohm headphone amp could use less supply V and lower output power to keep the chip from overheating

at the other extreme the TPA can be used with +/-16 V supply V, and swings to within ~1.5 V of each supply at "light" loads

1/2 * 14^2 / 300 = 320 mWrms into 300 Ohms

So the TPA6120 chip is capable of adequate drive of most headphones depending on how it is applied

 

[peranders]

TPA6120 is a nice sounding IC but beware of the input bias current which can cause you trouble since they are around 12 uA, instead of nA's. I have used the IC in my QRV07 amp.

 

[jcx]

yes, buffering the input of the TPA is a good idea with most audio source being AC coupled the required input-gnd resistors become noticeable loads to the source

I think the better approach once you've committed to 2 op amps/channel is to multiloop with the better and more powerful TPA replacing Walt Jung's favorite (old) AD811 inside the input "audio" op amp feedback circuit in his multiloop amp circuits

 

[odigg]

Quote:

Originally Posted by jcx /img/forum/go_quote.gif as always in engineering the answer is "it depends" in this case on power supply V and heatsink capacity the TPA6120 can put out 400 mA 1/2 *.4^2 * 32 = 2.5 Wrms into 32 Ohm load (with > +/-14 V supply) t the other extreme the TPA can be used with +/-16 V supply V, and swings to within ~1.5 V of each supply at "light" loads 1/2 * 14^2 / 300 = 320 mWrms into 300 Ohms So the TPA6120 chip is capable of adequate drive of most headphones depending on how it is applied

Why do you have the 1/2 in there? I thought the formulas were P = (I^2)xR and P= (E^2)/R.

 

[peranders]

14 V is the peak value and the rms value is SQR(2) lower. Voltage in your case is 14/0.7. Ohms laws which is basic knowledge and you should study it if you are unsure.

 

[odigg]

Ahh..sorry. I had assumed it was 14v rms from a regulated supply.