TPA2034D1: TPA2034D1 gain alternation

Kazuki Kuramochi

Part Number: TPA2034D1
Other Parts Discussed in Thread: TINA-TI, TPA2032D1

Hello Professional,

My customer has question for TPA2034D1.

This device is fixed gain(4V/V) but they'd like to change the gain to 2V/V. Of course, I understand this device has the family device that has 2V/V gain but they have to used TPA2034D1 due to various circumstances.

I checked the datasheet and I though we can change the gain by the external input resister as follows.

Is above calculation is correct? If it is correct, could you provide detailed internal resister's value?
Also is there any important points for above use case?

By the way, I run simulation on TINA-TI using uploaded reference sim file on ti.com.
I got probable transient simulation result but I cannot got the probable AC simulation result. it shows TPA2034's output gain is -140dB but transient simulation said it is 4V/V. Could you explain about what happen in the simulation?

I'm waiting hearing back from you.

Best regards,
Kazuki Kuramochi

over 4 years ago

0 Luis Fernando Rodriguez S. over 4 years ago

TI__Guru* 84915 points

Hi, Kuramochi-san,

We will need to confirm this with the team. In the meantime, could you tell me where did you get the gain calculation that you mentioned in the drawing? In addition, could you share your TINA-TI simulation, please? This is to have a better approach to this issue.

Thank you.

Best regards,
Luis Fernando Rodríguez S.

0 Kazuki Kuramochi over 4 years ago in reply to Luis Fernando Rodriguez S.

TI__Expert 8330 points

Hi Luis-san,

Thank you for your prompt reply.
This gain calculation is from my assumption based on functional block diagram.
Also, In simulation, output voltage would be a half when I input the 18.5kohm external resister as R1.

As for TINA-TI simulation, this question was solved by my self right now. I tried to do AC simulation but TP2034's model on ti.com is transient model. So I couldn't got a probable result.

I'm looking forward to hearing the feedback from you and your team.

Best regards,
Kazuki Kuramchi

0 Kazuki Kuramochi over 4 years ago in reply to Kazuki Kuramochi

TI__Expert 8330 points

Hi Luis-san,

Sorry for rushing your but do you have update for this?

Best regards,
Kazuki Kuramochi

0 Luis Fernando Rodriguez S. over 4 years ago in reply to Kazuki Kuramochi

TI__Guru* 84915 points

Kuramochi-san,

Your calculation is correct the equation that you mentioned above will be useful to reduce the device gain as you are looking for. I also attach this document about the fully-differential amplifier in case you search for additional information.

http://www.ti.com/lit/an/sloa054e/sloa054e.pdf

Best regards,
Luis Fernando Rodríguez S.

0 Kazuki Kuramochi over 4 years ago in reply to Luis Fernando Rodriguez S.

TI__Expert 8330 points

Hi Luis-san,

This device is not ordinal differential Amp, it is differential Class-D Amp. Also datasheet only explained the resister value of Ri1. So we cannot calculate the gain correctly. In the simulation, gain would be a half when I use 18.5kohm on R1. It seems total gain is defined by the first differential Amp stage from the point of view of simulation result. Is this correct?
In addition, is there any concern of this gain modification? I think this is not popular use case therefore I'd like to confirm about whether there is concern on this.

Best regards,
Kazuki Kuramochi

0 Luis Fernando Rodriguez S. over 4 years ago in reply to Kazuki Kuramochi

TI__Guru* 84915 points

Hi, Kuramochi-san,

We don't fully recommend to modify the amplifier gain since it was designed to use a fixed gain. As stated in the datasheet, it was designed to achieve a gain range from 11.5dB to 12.5dB. You can add resistors to modify the gain, but we cannot guarantee that the performance and the device behavior will be the same.

Instead, I would suggest to go for the TPA2032D1. It has a fixed gain of 2 V/V and it is pin to pin compatible with the TPA2034D1.

Please let me know if you have additional questions or comments on this.

Best regards,
Luis Fernando Rodríguez S.

0 Kazuki Kuramochi over 4 years ago in reply to Luis Fernando Rodriguez S.

TI__Expert 8330 points

Hi Luis-san,

I understand we cannot recommend such a use case and we have 6dB gain device(TPA2032D1).
However, Our customer would like to how to change the gain from the point of view of technical side. Of course, they understand our information is just a information and TI don't guarantee.
Could you provide the R1 value which set the gain as 6dB? I think this is 18.5kohm. Is this correct?

Best regards,
Kazuki Kuramochi

0 Luis Fernando Rodriguez S. over 4 years ago in reply to Kazuki Kuramochi

TI__Guru* 84915 points

Hi, Kuramochi-san,

You are right, 18.5Kohms value would be enough to set the gain as 6dB.

Best regards,
Luis Fernando Rodríguez S.

0 Kazuki Kuramochi over 4 years ago in reply to Luis Fernando Rodriguez S.

TI__Expert 8330 points

Hi Luis-san,

Thank you for your support.
I understand.

Best regads,
Kazuki Kuramochi

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TPA2034D1: TPA2034D1 gain alternation