Design Methodology for MFB Filters in ADC Interface Applications

(ACTIVE) MFBFILTER-CALC

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MFBFILTER-CALC:
Design Methodology for MFB Filters in ADC Interface Applications

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Description

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While the Multiple FeedBack (MFB) filter topology is well-known, its application to very high dynamic range analog-to-digital converter (ADC) interfaces requires a careful consideration of component value selection. This application report develops the ideal transfer function, then introduces a component selection methodology and discusses its impact on noise and distortion. The impact of the amplifier Gain Bandwidth Product on final pole locations is also included, showing several examples. A complete high dynamic range, differential I/O filter for wide dynamic range ADC driving is then designed. A simple design spreadsheet embodying this design approach is available for download with this application report.

Features

The spreadsheet comprises five related worksheets:

  1. MFBdesign: This worksheet allows the user to select a part number, set target filter specifications, and design the component values. This design sequence has been shown in the examples used in this application note.
  2. PartSelection: This worksheet contains the list of amplifiers with their required specifications and allows the designer to select a part and then load the needed data in the MFBdesign sheet. The part number must be entered in the MFBdesign sheet exactly as listed here (NOTE: Selection is case-sensitive). Also, this sheet shows the resulting loop gain plots and final phase margin. This sheet is where a CT value would be selected for noise gain control if a non-unity-gain stable amplifier is selected.
  3. NoiseGainPlot: The noise gain calculations are performed on this worksheet, with the plot replicated in the PartTable sheet.
  4. PartAolgain: Each of the device open-loop gain over frequency values are tabulated.
  5. PartAolphase: Each of the device open-loop phase values are tabulated.

Technical Documents
Application notes (1)
Title Abstract Type Size (KB) Date Views TI Recommends
Multiple Files   23 Feb 2005 324

TI Devices (28)

Part Number Name Product Family
OPA131  General Purpose FET-Input Operational Amplifiers  Operational Amplifiers (Op Amps) 
OPA227  High Precision, Low Noise Operational Amplifiers  Operational Amplifiers (Op Amps) 
OPA228  High Precision, Low Noise Operational Amplifiers  Operational Amplifiers (Op Amps) 
OPA2613  Dual Wideband, High-Output Current, Operational Amplifier with Current Limit  Operational Amplifiers (Op Amps) 
OPA2614  Dual, High Gain Bandwidth, High Output Current, Operational Amplifier with Current Limit  Operational Amplifiers (Op Amps) 
OPA2822  SpeedPlus Dual Wideband, Low-Noise Operational Amplifier  Operational Amplifiers (Op Amps) 
OPA340  Single-Supply, Rail-to-Rail Operational Amplifiers MicroAmplifier™ Series  Operational Amplifiers (Op Amps) 
OPA350  High-Speed, Single-Supply, Rail-to-Rail Operational Amplifiers MicroAmplifier™ Series  Operational Amplifiers (Op Amps) 
OPA355  2.5V, 200MHz GBW, CMOS Single Op Amp With Shutdown  Operational Amplifiers (Op Amps) 
OPA627  55V/µS, High-Speed, 0.8µV/˚C Drift Max, Precision Operational Amplifier  Operational Amplifiers (Op Amps) 
OPA637  Precision High-Speed Difet® Operational Amplifiers  Operational Amplifiers (Op Amps) 
OPA656  Wideband, Unity Gain Stable FET-Input Operational Amplifier  Operational Amplifiers (Op Amps) 
OPA657  1.6GHz, Low Noise, FET-Input Operational Amplifier  Operational Amplifiers (Op Amps) 
OPA690  Wideband, Voltage Feedback Operational Amplifier With Disable  Operational Amplifiers (Op Amps) 
OPA727  e-trim 20MHz, High Precision CMOS Operational Amplifier  Operational Amplifiers (Op Amps) 
OPA820  Unity Gain Stable,Low Noise,Voltage Feedback Operational Amplifier  Operational Amplifiers (Op Amps) 
OPA830  Low-Power, Single-Supply Operational Amplifier  Operational Amplifiers (Op Amps) 
OPA842  Wideband, Low Distortion, Unity Gain Stable, Voltage Feedback Operational Amplifier  Operational Amplifiers (Op Amps) 
OPA843  Wideband, Low Distortion, Medium Gain, Voltage Feedback Operational Amplifier  Operational Amplifiers (Op Amps) 
OPA846  Wideband, Low Noise, Voltage Feedback Operational Amplifier  Operational Amplifiers (Op Amps) 
OPA847  Wideband, Ultra-Low Noise,Voltage Feedback Operational Amplifier with Shutdown  Operational Amplifiers (Op Amps) 
THS4031  100-MHz Low Noise Voltage-Feedback Amplifier  Operational Amplifiers (Op Amps) 
THS4130  Fully Differential Input/Output Low Noise Amplifier With Shutdown  Operational Amplifiers (Op Amps) 
THS4271  Super-Fast Ultra-Low Distortion High Speed Amplifier  Operational Amplifiers (Op Amps) 
THS4502  High-Speed Fully-Differential Amplifiers  Operational Amplifiers (Op Amps) 
THS4508  Wideband Fully Differential Amplifier  Operational Amplifiers (Op Amps) 
THS4511  Wideband, Low Noise, Low Distortion Fully Differential Amplifier  Operational Amplifiers (Op Amps) 
THS4631  High Speed FET-Input Operational Amplifier  Operational Amplifiers (Op Amps) 

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