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INA826: low amplitude signal transmission on 25mts cable

Kiran Gopalaiah
Intellectual 710 points
Part Number: INA826
Other Parts Discussed in Thread: DRV134, DRV135, DRV632, DRV603

Hi,

Greetings !!

Need help to understand how effective the below scheme is for converting single ended signal to  differential and transmitting  the same on a shielded, twisted pair for a distance of 25 mts. ( The scheme is suggested by a TI employee and has asked me to get it reviewed as he is not  well-versed with INA 826)

Requirements

1) signal is a pulse in the range of 250 mV  to 4.5 V and  frequency ranges from 1 KHZ to 9 KHz .

2) media of transmission : 25 mts.shielded, twisted pair

2) For my application I prefer to use dual supply opamp (+/-5V)

3) ESD and Noise protections are necessary

4)) what is the error in the amplitude I can expect ( is it within 2 to 3%) ?

5) How do I arrive at the % error in amplitude ?

Regards

  • 0
    Guru 140200 points
    Hi Kiran,

    TI has sepcial audio line drivers for this purpose:

    www.ti.com/.../products.html

    One mistake of your scheme which I immediately see is that a current path to signal ground for the input bias currents of U4 is missing. See section 8.3.6 of datasheet of INA826.

    Kai
  • 0 in reply to kai klaas69
    Intellectual 710 points
    Hi Kai

    Greetings !!

    Noted the mistake, need to add resistors to provide necessary bias

    Referred the audio line driver data sheet. I do no have any experience in this area. Kindly help me to understand what are the parameters to be considered while selecting a line driver? The system requirements are as already mentioned. One more point I need to make is that the bandwidth of the signal to be transmitted is 150 KHz .Likely to increase upto 220 KHz is the future .
  • 0 in reply to Kiran Gopalaiah
    TI__Guru* 95225 points

    Hi Kiran,

    You can select one of our Line Drivers based on your application requirements.

    If you need single-ended input and differential output, you can consider DRV134/DRV135.
    If you need differential input and single-ended output, you can consider DRV603 or DRV632

    Single-ended output devices feature an internal charge-pump to generate the negative supply rail, so you don't need double supply or output coupling capacitors.

    As Line Drivers are purposed for cable transmissions, these include some specs related to relatively high impedance and capacitive loads.

    If you have some further questions about one of our devices, please post a new thread with your questions and the part number.

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators

  • 0 in reply to Ivan Salazar
    Intellectual 710 points

    Hi Ivan Salazar,

    Thanks for the inputs.