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Why should we use an amplifier to amplify the small signal before analog to data convert?

user4768469
Intellectual 290 points
Other Parts Discussed in Thread: ADS1298

Hi，

Usually,we use an amplifier to amplify the small signal(<1V or more less) before an ADC converter,there are some questions as below:

1.What's the definition of small signal?

2.If not use the amplifier,can the ADC acquire the small signal directly? In What case,the ADC can acquire the signal directly?

Thanks!

  • 0
    TI__Guru**** 180791 points
    Hi there!

    Is there a specific part number that you are looking at? "Small signal" does not necessarily mean something with <1V of magnitude - in general terms, its got more to do with how transistors are biased inside the amplifier circuit to maintain linear operation. Many of our Delta-Sigma data-converters have internal programmable gain amplifiers (PGA's) that can be directly interfaced with 'small signals' so that there is no need for a gain stage ahead of the device. For example, our ADS1298 is meant for use in ECG applications, where the signals are typically only a few millivolts in amplitude. The internal PGA on that device can provide gain up to 12V/V.