AnsweredAssumed Answered

AD8337 Evaluation Board Fig 82, DC couple, Single Supply Biasing

Question asked by analord on Jan 11, 2017
Latest reply on Jan 12, 2017 by jstaley

Hello,

 

Amplifying a signal from a TIA powered from 5V.  The signal swings from ~0V up to ~3V depending on received light intensity. I am looking to DC couple the TIA to the AD8337 and would like to ask and verify the following:

 

Regarding the Single Supply AC coupled Design shown in Figure 82:

  1. Why is RFB1 connected to the output of the 2.5V reference?
  2. Why is R1 connected to the 2.5V Reference and not Ground?  
        -I realize the R1 must connect from INPP to INPN for AC coupling, however would like clarification as to why this is so.
  3. If it was desired to DC couple this device in single supply mode is the following correct:
    • Remove C6 and R1
    • Connect RFB1 to Ground 
      • Could connecting RFB1 to ground create a large DC offset at VOUT?

  4. A lead/lag comp is feeding pin 7 GAIN, what us the purpose of CG?

    Thanks for the assistance.

Outcomes