Hi --

I have a CMOS chip and I generate a square wave with changing frequency. It is LVTTL (3.3Volt) and max current from the device is 24mA.

I want to drive a speaker in both directions with it so I added a capacitor such that RC>>Frequency of my square wave (I think this method is called coupling capacitor?). That worked and produces a nice AC square wave -3 to 3 volts.

Now I want to amplify this AC square wave so I can get up to 250mW for my speaker.

I can see how to amplify current for a DC square wave with a single transistor but how do you amplify an AC square wave? Can it be done with simple transistor amplifier? Do I need an Op Amp (but looking at those it seemed like they are not the right choice for driving a speaker?)

I did a lot of searching on the Internet for how to do this but nothing seemed right so I am posting here.

Thank you!

 

I answered your questions on another website.

 

I answered your questions on another website.

could you give the link of your another website?

 

could you give the link of your another website?

http://www.electro-tech-online.com/general-electronics-chat/88424-how-amplify-ac-sqaure-wave.html

 

I answered your questions on another website.

I know how you feel.

I once have a case where the OP ask the same question again on another website but with comments like "Some guys told me to use/do xxxx, what do you guys thinks".

I nearly replied "That's rubbish, don't listen to a single word he said."

Sorry to OP for hijacking the thread.

 

Use an op amp to amplify the voltage and then use a transistor in an emitter follower configuration to drive the speaker. The best solution, however, will be an audio amplifier. Have a look at www.national.com for audio amplifiers integrated in a chip.