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  • TI Thinks Resolved

DRV134: DRV134

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Replies: 14

Views: 591

Part Number: DRV134

Hi there / i wander if i can use the DRV 134 after the INA 134 without a buffer between them. the INA134 receiver to convert balance signal into unbalance, then to ed just the volume for my needs, and then bring it back to balance with the DRV134.

Thank you in advance

ilan  

  • In reply to Andy Peters:

    Hi Andy,

    Thanks much for relating your experience with the DRV134. The information should prove helpful to others considering similar applications for the DRV134.

    Regards, Thomas
    Precision Amplifiers Applications Engineering
  • In reply to user5932320:

    Hi Ilian,

    1- In the datasheet of the DRV134 and INA134 you suggest to use 1uf capacitors between ground and +/- Vcc/Vee. Isn’t it better to use smaller size of ceramic capacitor such as 100pf?

    The power supply bypass capacitors should exhibit a very low impedance in the operating frequency range, in this case the audio frequency range. The low impedance shunts ac and noise riding on the dc power supply level reducing their level. The large bypass capacitor serves as a charge reservoir during intended transient output events when the DRV134 needs to very quickly supply current to a load.

    A 100 pF capacitor has about 1.5 Megohms of capacitive reactance at 1 kHz so it is not an effective bypass in the audio frequency range.

    2- What is the function of the 300 ohm resistors at the outputs of the DRV134 (RL1, RL2)?

    The 300 ohm resistors were in the original TINA TI Reference Design circuit. They also are used in datasheet Figure 25, the Output Common-Mode Rejection Test Circuit, so I left them in for the simulation. It doesn't mean they are necessarily needed for all applicaitons.

    The DRV134 datasheet shows R1 (RL1), R2 (RL2) and a differential RL being applied in the various circuits. The DRV134 outputs can drive a 600 Ohm load to 17 VRMS and that is an important point. Figure 29, a Complete Audio Driver and Receiver Circuit, doesn't include the load resistors and simply drives a twisted pair line connected to the input of INA134 receiver. When driving very long cables have a characteristic impedance of 600 Ohms it may be beneficial to terminate the line in a 600 Ohm load, and the DRV134 can deliver the current.

    An important point about including, or not including the resistors in the circuit can be observed by viewing the THD + noise (%) graphs in datasheet section 7.4. The curves on the graphs indicate that without the load resistors the THD + noise (%) is highest above 1 kHz compared to when they are present in some form. Adding a 600 Ohm resistor from each output to ground improves the THD + noise compared to when they are not used. And the best THD + noise is obtained when the 600 Ohm differential load resistor is used alone. Therefore, the THD + noise performance is an important factor in determining their use.

    Regards, Thomas

    Precision Amplifiers Applications Engineering 

  • In reply to Thomas Kuehl:

    Thank you, what OP buffer could feet to work smoothly with the ina134 and the drv134?

    Thank you ' ilan

     

     

  • In reply to user5932320:

    Hi Ilian,

    Here are links to two of our SoundPlus audio op amps, and one industrial op amp that should provide very good audio performances in your application. Note that the OPA1652 is a dual op amp and you may not need the extra channel. Both the OPA1641 and the OPA172 are single channel op amps.

    www.ti.com/.../OPA1652

    www.ti.com/.../OPA1641

    www.ti.com/.../OPA172

    Regards, Thomas
    Precision Amplifiers Applications Engineering

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