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FM demodulation of differential signal.

Alex_Bam

Sep 28, 2020
25
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Sep 28, 2020
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Hello everyone,
I am designing LPF based differential demodulator(LPF_DDM) to retrieve differentially modulated signals, which are on-chip capacitive isolated [shown]. LPF_DDM includes a differential amplifier, LPF, and Schmitt trigger. I designed a two-stage opamp [specification below], as a differential amplifier. Simulation results of the 2-stage opamp matched with desired specifications (GBW, Phase margin, gain, etc ), however when the differential modulated signals are given as input, then opamp does not work.
Is my 2-stage opamp design and/or design parameters adequate for differential modulated input signal?

Thanks.

Design Parameters:
Input common mode range: ICMRmax = 4V; ICMRmin = 1.5V ; Load capacitance =2pF ; Gain = 1000/60db ; Slew-rate (SR) = 20v/usec. GBW=30MHz
Phase margin (PM)>= 60-degree
 

Attachments

  • Schmatics of 2-stage Opamp.JPG
    Schmatics of 2-stage Opamp.JPG
    24.3 KB · Views: 6
  • Simulation result of 2-stage Opamp.JPG
    Simulation result of 2-stage Opamp.JPG
    122.3 KB · Views: 4
  • Result when diffenentail signal is given as input.JPG
    Result when diffenentail signal is given as input.JPG
    134.5 KB · Views: 4
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