TINA/Spice/TLV9062: noise simulation of 2 stage bandpass filter

Cera Wei

Intellectual 2010 points

Part Number: TLV9062
Other Parts Discussed in Thread: TINA-TI

Tool/software: TINA-TI or Spice Models

Hi,

I'd like to simulate the noise by TINA, the circuit is as below. There are 2 stage pass band filter, and the parameters of each stage are the same. The high pass corner frequency is about 110Hz, and the low pass frequency is about 1.3kHz, the gain of each stage is 120.

The noise of first stage at VF1 is about 120uV, the same as I calculated by hand. For the second stage, the gain is 120, the first stage noise should be amplified by 120 and at least 120*120uV=14.4mV. Why the total noise at VF2 is only 10.59mV?

I have checked the bode plot, the gain and the corner frequency is as expected.

Could you please help me? Thank you！

over 6 years ago

0 Ron Michallick over 6 years ago

TI__Guru*** 139956 points

Cera,

Can you send the attachments again? They did not work in your last message.

0 Cera Wei over 6 years ago in reply to Ron Michallick

TI__Intellectual 2010 points

hi, Michallick,

Thank you for your reply.
There's something wrong with the figures, sorry for that. I have posted the figures again.

Regards,
Cera

0 RJ over 6 years ago in reply to Cera Wei

TI__Intellectual 2550 points

Hello Cera,

Thank you for uploading your figures again for us. I will look into this and get back to you as soon as possible.

Regards,
Ramon

0 RJ over 6 years ago

TI__Intellectual 2550 points

Hello Cera,

Your output noise signal at VF1 is amplified by the noise gain on the third stage, not the signal gain. The remaining region is attenuated as shown in the image below.

Please let me know if there is anything else I can assist you with.

0 Ron Michallick over 6 years ago in reply to RJ

TI__Guru*** 139956 points

Cera,

The noise plot from Tina seems to be adding (accumulating) up the noise from low to high frequency. Therefore only the final value has meaning as an amplitude. The amplifiers filter out low and high frequencies (less gain) so later amps will amplify some noise frequencies less than others. Therefore the final noise will be less input noise times peak gain.

0 Cera Wei over 6 years ago in reply to Ron Michallick

TI__Intellectual 2010 points

Hi, Ronald,

Thank you for your help, I got it.

Best regards,
Cera

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TINA/Spice/TLV9062: noise simulation of 2 stage bandpass filter