connect LM324 to an 8 ohm speaker

Thread Starter

alexpanrui

Joined Feb 25, 2008
32
dear all,
anyone could help me with the connection between a LM324 and an 8 ohm speaker...thx a biiiiiiiiiiiiiiiillion
 

Papabravo

Joined Feb 24, 2006
16,498
I don't think an LM324 has the schtutz to drive a speaker directly but it would start with a blocking capacitor to the speaker to ground.
 

Thread Starter

alexpanrui

Joined Feb 25, 2008
32
thank both of u for the quick reply...but the chip lm324 is provided by my lecturer...so i guess i have to use it...papabravo, i dont get u...i'm pretty new to circuit design...thx
 

Papabravo

Joined Feb 24, 2006
16,498
thank both of u for the quick reply...but the chip lm324 is provided by my lecturer...so i guess i have to use it...papabravo, i dont get u...i'm pretty new to circuit design...thx
What's not to get? How much current can an LM324 source or sink. Is enough to move the voice coil?
 

Audioguru

Joined Dec 20, 2007
11,249
An LM324 can output a peak current of 20mA. The RMS current is 14.1mA and the RMS power into an 8 ohm speaker is only 1.6mW. Earphones are much louder.

The LM324 "power amplifier" applies a bias voltage of 6V to the speaker that might push the cone so far out of the magnetic gap that the speaker will perform like a rectifier.
The DC current is high enough to melt a little speaker.
 

Papabravo

Joined Feb 24, 2006
16,498
An LM324 can output a peak current of 20mA. The RMS current is 14.1mA and the RMS power into an 8 ohm speaker is only 1.6mW. Earphones are much louder.

The LM324 "power amplifier" applies a bias voltage of 6V to the speaker that might push the cone so far out of the magnetic gap that the speaker will perform like a rectifier.
The DC current is high enough to melt a little speaker.
You know these things, and I know these things, and many other forum members know these things. I was kinda hoping the OP would discover these things on his own. He seemd to have just a modicum of industry.
 

Thread Starter

alexpanrui

Joined Feb 25, 2008
32
yo,thank u all...finally i heard something from the speaker...and one more thing i wanna clarify is that MY LAB OFFICER FORGOT TO GIVE ME LM386!!!!!!!!!!!!!!!!!!!!!!!!I bought one and am testing it now...basically the analog output is from DAC0832...I connect this output to LM324 which is working as a voltage follower (buffer)..and i fed the output from LM324 to LM386 which drives an 8 ohms speaker....i can hear something from the speaker,but the sound doesnt sound ok.....its like siren alarm...ive wrote a small piece of program which feeds in 0x00 and 0xff to DAC continuously...shouldnt the sound be consistent?wat could be the problem???
 
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