PGA460-Q1: Adding external amplifier for the receiver circuit

Hi user,

Have you tried using all of the following gain features of the PGA460 before trying to use the external amplifier:

• Time varying gain (described in section 7.3.3 of the datasheet): This gain feature can apply a receiver gain from 32 to 90 dB
• Digital Gain (described in Section 7.3.4.5 of the datasheet): Applies either a x1, x2, x4, x8, x16, or x32 gain
• Nonlinear scaling (Section 7.3.4.3 of the datasheet): This feature can implement the following gain function:
  • if (t < Time _ Offset):
    • Output= Input;
  • else
    • Output = (Input – Noise_Level)^{Scale_Exponent}

For most applications, the above gain options are more than enough for sensing small signals. 

Another option is to use the TUSS4470 or TUSS4440 device instead, which both have a logarithmic gain amplifier that provides larger gains for smaller input signals.  The below application note provides more details on the logarithmic amplifier on the TUSS44x0 devices:

https://www.ti.com/lit/an/slda053/slda053.pdf?ts=1619633328844&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FTUSS4440

Regards,

Mekre

Thank you for the reply.

As for the TVG, we are setting it at 90 dB (where we want to detect the faintest signal).

As for the digital gain, in my understanding, varying it is equivalent to varying the threshold level. Is that correct?

I'll look into the options of using other ICs.