TPA6120A2: Anplifier clipping problem

Hello,

Can you clarify here if this is a purely resistive load that you are introducing? or it the speaker that is shown in the schematic, and if the speaker can you provide a datasheet or equivalent model of the speaker? 

Just looking through the schematic there doesn't seem to be any glaring issues that would expect that type of response.

Best,

Hasan Babiker

Thanks for your reply. It turns out to be a faulty amplifier, swapped it with the new one and it works fine now.

However there are some quirks working with single supply. I have this schematic laid out on the breadboard and the virtual ground has a path to the amplifier few inches long. It seemed like it started to oscillate and distort the output. I added a 100nF capacitor from Opamp + input (LIN+) to ground and that seemed to help. Do you have any advice how to better wire up my schematic, should I also add a capacitor from LIN+ to 24V also? Should I use larger capacitor?

Hello,

You mention that you are getting some distortion when using single supply. For clarification, that output works as expected when used in a single-supply configuration?

Best,

Hasan Babiker

Yes it  seems to work with sine wave. I have not had a chanche to connect the speaker yet though. But only as long as i connect a capacitor close to the noninverting input. I just want to be sure it is the correct way to use it since datasheet does not mention single supply anywhere.

Hello,

It looks like I mistyped in my previous response, I meant to ask does the device work in a dual supply config? There shouldn't be an issue in using the TPA6120A2 in single-supply as long as you are remaining within the input/output limits of the device... can you provided images of this distorted output and describe the characteristics of your input?

Best,

Hasan Babiker

I have attached an image with capacitor in + input and without. There is a slight distortion, interestingly on both signals, input and output. I kind of remember it being worse before.

Actually another question arised. The TL0742 seems to be clipping the signal at around 17-18V. Even though the supply voltage is 24VDC. If I disconnect the TPA6120 from the preamp(disconnect R37), the clipping disappears. Any idea why it happens? Is TL0742 a right type of opamp to drive TPA6120?

See following picture, yellow line is TL072 invering input(through 20k resistor), and blue line is TL072 output (left side of R37).

Hello,

The TPA6120 is sensitive to parasitics and distortion & oscillations can be expected without proper layout. Please note section 12 of its datasheet.

In regards to the TL074, if you take a look at table 6.21 of the datasheet the output swing has a minimum of +/- 10V for a +/-15V supply. By reducing the load further to 1kohm this swing can be reduced even more. The upgraded TL074H seems to be able to swing a lot closer to the rails. 

Best,

Hasan Babiker