ADC input configuration with transformer in front end

[engr_joni_ee]

Hi,

I have seen some examples where a single ended analog signal is converted to differential using a transformer and then a differential operational amplifier is used before it reach the ADC analog differential input.

I have some basic questions when the signal passes through transformer.

1-Do we get the same frequency components at the output of transformer ?
2-What we lose and what we get if the number of turns are same in the primary and secondary coils ?

 

[KlausST]

Hi,

1) Basically yes. There is a lower frequency limit, mainly because of core saturation. In this case you lose amplitude of the fundamental and increase amplitude of overtones (distortion).
2) you get galvanic isolation and get reduced influence of induced noise (differential system, cancelling common mode noise).
You lose a bit of precision. There are lower frequency limits and there are upper frequency limits.
The core will cause remance and hyteresis problems.

Klaus

 

[FvM]

You'll know if you check the transformer specification.

 

[engr_joni_ee]

Hi,

Do the transformers have SPICE models which we can add the in LT Spice to simulate with the signal model ? I am looking for the SPICE models of ETC1-1-13 and
ADT1-1WT.

 

[FvM]

These are Macom respectively Minicircuits parts, they come with s-parameters, but no SPICE models. They might be fitted to the s-parameter tables.

 

[engr_joni_ee]

Now I have got the S parameters of both components from Macom and Minicircuits websites. How can I convert these S parameters into SPICE model so that I can add them in simulation in LT Spice ?