LM4950: LM4950

Muhammad Faisal

Part Number: LM4950

Hi,

I am using LM4950 audio amplifier with DAC to amplify my audio signal. The output of the LM4950 is connected to the transformer and the output of the transformer is connected to ultrasonic transducer.

The shutdown pin is continuously high, which means that the amplifier is continuously on.

I generate 10ms of chirp signals (ultrasonic range > 20kHz) which repeats after every 300ms.

When I play the sound, I hear some clicks from the amplifier even I am not turning on and off the amplifier. At the output of the transformer, the signal is also distorted.

Can somebody explain why am I hearing the sound and how can I remove it?

Best Regards

over 8 years ago

0 José Luis over 8 years ago

TI__Mastermind 20085 points

Hi Muhammad,

This device isn't used for ultrasonic applications. I recommend you to search an adequate device in our product folder of ultrasonic sensing on ti.com
Let me know your thoughts.

Best Regards
José Luis Figueroa
Applications Engineer

0 Muhammad Faisal over 8 years ago in reply to José Luis

Prodigy 120 points

Hi,

I also checked it for 15kHz - 18kHz frequency but still I can hear clicks from the amplifier.

Quite confused :/

Regards

0 Muhammad Faisal over 8 years ago in reply to Muhammad Faisal

Prodigy 120 points

Hi,

I checked my circuit again today. I removed the transformer and I found out that the clicking sound was completely gone. I also checked the signal at the output of the amplifier and it was also not distorted.

I am not sure why is the transformer distorting the signal and also the clicking sound? Any idea?

Regards

0 José Luis over 8 years ago in reply to Muhammad Faisal

TI__Mastermind 20085 points

Hi Muhammad,

I think that the device is having problems due to saturation of the transformer core. You can have a look at the next application report: Audio Power Amplifier Operation with Transformer Load. Here you can find further information about this.

Best Regards
José Luis Figueroa
Applications Engineer

0 Muhammad Faisal over 8 years ago in reply to José Luis

Prodigy 120 points

Hi,

When I reduced the input voltage, the clicking sound is removed. Initially, the input voltage to the transformer was 6Vp and when reduced to 5Vp it worked perfectly fine.

So yeah I guess the transformer core gets saturated at higher input voltage.

Thanks your reply.

Regards

Audio

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LM4950: LM4950