Audio Amplifier Selection

[joersam24]

Hi to all,

I want to amplify an audio signal from the output of CODEC with a minimum line out resistance of 2k? and the output of the amplifier will feed to a dynamic receiver(earpiece) with an impedance of 150?. Can anyone suggests a suitable audio amplifier to be used? What should be the implementation? Do I need some impedance matching device?

I hope you can help me with this one. Thank you...

[Zero999]

The LM386 will probably do but you haven't mentioned the input/output levels.

[FenderBender]

Not exactly sure but a low noise op-amp would probably do.TL071, NE5532 or OPA2314.  A 150ohm headphone shouldn't take too much to drive.

LM386 would also work. THD figures might be a little higher?

[T4P]

150ohms is not a hard one to drive,
do you want a 1W headphone driver or you want a normal opamp ?
The NE5532 can drive down to 15 ohms load i think but it does have 38mA output short-circuited nominally
OR you can just shoot for a 1W headphone driver that is available only in weird packages but most phones use that

[ejeffrey]

There are many options for headphone amplifiers, from dedicated chips to opamps to discrete transistors.  All are capable of performing admirably.  One question was unaddressed:

Do I need some impedance matching device?

No, impedance matching is generally undesirable in audio applications.  The major exception is the analog phone system.  In general you want the output impedance much less than the input impedance it is driving.  So your amplifier should have an input impedance much greater than 2.2 kohm and an output impedance of much less than 150 ohm.  This is not hard to accomplish, just something you need to be aware of.

Is this a line-out from some existing equipment, or are you implementing the codec yourself?  If the latter, you will need some anti-aliasing filter.  The data sheet for the CODEC will help you out.

[FenderBender]

A popular project is a "cMoy" that you can look at for reference. It's just a non-inverting op-amp set up but there's loads of information on it. Some valuable, some audiophoolery. Either way. Might want to give it a glance.

[T4P]

A popular project is a "cMoy" that you can look at for reference. It's just a non-inverting op-amp set up but there's loads of information on it. Some valuable, some audiophoolery. Either way. Might want to give it a glance.

Yes but it uses audiophoolery-ish pricey parts like the Burr-brown OPA2134

[FenderBender]

True,any modern op amp would work

[joersam24]

Thank you everyone for your replies and suggestions... It really helps me as I'm a beginner in Electronics Design...