• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 48 subscribers
  • Views 422 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

low frequency single supply amplifier circuits

Bob Edwards
Prodigy 210 points

Other Parts Discussed in Thread: TLE2426, OPA350

Hello All,

A question from a novice. I have sensors which output low frequency ac signals (near dc to ~ 50Hz) which I want to amplify for use by A/D converters, and if possible I want the active circuit components to use a single polarity power supply. If I use a voltage divider and/or a TLE2426 rail splitter with a buffer to generate a virtual ground as I've seen written up, the advice I've seen suggests a capacitor in line with the input to the op amp to prevent the incoming ac from disturbing the virtual ground. However, it seems to me that any capacitor is going to decrease/distort the low frequency part of the input signal.

Any ideas or corrections to my misunderstanding would be greatly appreciated.

  • 0
    TI__Guru* 93105 points

    Hello Bob,

    The TLE2426 is referred to as a "rail splitter." It is most often used to establish a dc voltage that is 1/2 the volt level applied to the IN pin. Sometimes in operational amplifier circuits there is a need to bias the non-inverting input at a level equal to 1/2 the operational amplifiers V+ supply voltage. The TLE2426 is a convenient way to accomplish the task. It has a precision 1/2 divider at the input and a high-output current buffer that won't be loaded down like a high resistance, resistive divider. The addition of the capacitor to ground off the input pin to ground is intended to reduce noise in a dc application, but can couple an ac signal to ground if its reactance is low enough. Therefore, you probably wouldn't want to include the capacitor in an ac application unless its reactance is high relative to the measurement frequency.

    Note that the TLE2426 data sheet includes few ac specifications because of its primary use is as a dc splitter. You may want to consider using an actual rail-to-rail, input/output operational amplifier for the A/D driver. The specific operational amplifier would depend on the load the A/D converter and any interface presents to the amplifier. The OPA350 is an excellent A/D driver. It is a good choice when the signal-chain bandwidth is wide and the load capacitance is large (>1nF).

    Regards, Thomas

    PA -Linear Applications Engineering