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OPA320: We need Low Noise Amplifier & PGA with 1dB gain variation

Lakshmanan V
Intellectual 480 points
Part Number: OPA320
Other Parts Discussed in Thread: OPA192, PGA202, PGA2500, PGA204, ADS1274
Hello sir,

We are working on New project called 4-Channel ADC card

Please suggest me relevant part for  following section. The Requirements are

1). Low Noise Amplifier spec.

Voltage Noise : 10 nV/√Hz

Current Noise : 1 fA /√Hz

Very low input bias current

Fixed Gain : 40 dB

2). Charge Amplifier spec.

Voltage Noise : 10 nV/√Hz

Current Noise : 1 fA /√Hz

Very low input bias current

Fixed Gain : 40 dB

3). Programmable Gain Amplifier spec.

Variable gain of 0  to 60 dB with minimum gain step variation 1dB.

Minimum Supply Voltage : ±2.5V

4). Anti-aliasing Filter spec

4 or 8th order Elliptical LPF Filter or Butter-worth LPF Filter with unity gain

Cutoff frequency: 4 kHz

5). 4-Channel 24-bit ADC spec

24-Bit resolution

Support Simultaneously-Sampling

support minimum Sampling rate : 12.8 kHz

Suggest me the op-amp, PGA & 24-Bit ADC relevant part for above specification.

Hereby enclosed our project Block diagram for your reference.

4 channel Data Acquisition Card block diagram.pdf

Note:- Supply Voltage for all op-amp signal conditioning section work with ±2.5V or ±5V

Regards

Lakshmanan V

  • 0
    TI__Guru 63640 points
    Lakshmanan,
    A signal bandwidth is a function of the close loop-gain - please provide information regarding required bandwidth, IQ, Vos, output drive, input common-mode and output voltage range, etc. for 1) and 2) op amp.
  • 0 in reply to Marek Lis
    Intellectual 480 points
    Hello sir,


    Low Noise Amplifier & Charge Amplifier should have following specifications

    1).Low input bias current < 2 pA
    2). Low offset voltage < = 50 µV
    3). Offset voltage drift: ±0.13 µV/°C typical, ±0.5 µV/°C maximum.
    4). Low voltage noise density <= 14 nV/√Hz at 10 kHz
    5). Interested bandwidth: 0 to 20 kHz with gain =100.
    6). Supply Voltage ±5V.
    7). Input Voltage Range > ±3 volts.
    8). Rail to Rail output.


    Regards
    Lakshmanan V
  • 0 in reply to Lakshmanan V
    Intellectual 480 points
    Hello sir,


    Please Ignore the above mail.


    Low Noise Amplifier & Charge Amplifier should have following specifications

    1).Low input bias current & Input offset current < 2 fA
    2). Low offset voltage < = 50 µV
    3). Offset voltage drift: ±0.13 µV/°C typical, ±0.5 µV/°C maximum.
    4). Low voltage noise density <= 14 nV/√Hz at 10 kHz
    5). Interested bandwidth: 0 to 20 kHz with gain =100.
    6). Supply Voltage ±5V.
    7). Input Voltage Range > ±3 volts.
    8). Rail to Rail output.

    Regards
    Lakshmanan
  • 0 in reply to Lakshmanan V
    TI__Guru 53596 points

    Hello Lakshmanan,

    Most CMOS amplifiers will have input bias currents in the picoamperes range.  The  OPA192 will work with the dual +/-5V supplies, offers rail-to-rail output, meets the low offset (+/-25uV max) and low offset drift (+/- 0.1uV/C typ) requirement, and noise 5.5nV/(sqrt(Hz) and exceed  bandwidth requirements (0-20kHz) with gain of 100.  However ,the max input bias current is +/-5pA typ (20pA max); which is typical on a CMOS input amplifier.

    There is a Difet - ultra low bias current amplifier, the OPA129, but it will not meet your other specifications.

    3)  I don't believe there is a off the shelf PGA that will meet 0-60dB gain with 1-dB steps.  There is a couple of legacy devices that  will offer PGA gains 0-60dB, on decade steps (PGA204, PGA202).  The PGA2500 is a microphone preamplifier that offer gains of 10dB-65dB in 1dB steps.

    4)  You could consider designing a custom 4th order active filter that will meet your spec.  A couple of tools that may help you with the design are Filter Design Tool and TINA TI SPICE Based analog simulation program.

    Thank you and Regards,

    Luis

  • 0 in reply to Luis Chioye
    TI__Guru 53596 points

    Hi Lakshmanan,

    A possible suggestion for a delta-sigma ADC with 24-Bit resolution and offering 4-channel simultaneous sampling is the ADS1274.  It offers 70-kHz bandwidth.  There may be other options.  Please submit your query in the Data converters Forum for additional queries on ADCs.

    Thank you and Regards,

    Luis