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LMC662: LMC662

Guy Painchaud
Prodigy 10 points
Part Number: LMC662

Tool/software:

I am simulating the following circuit using the LMC662A.MOD, LMC662B.MOD Spice models.  Capacitor C1 sets the low frequency cutoff while C2 sets the high frequency cutoff.  With C2=0, I see the full frequency response of the amplifier.  With C2=1.2nF, I initially see a cutoff of ~13.1 kHz, but it is not monotonic roll-off.  So other polls and zeros in amp model.  How do I obtain a monotonic roll-off ???

Circuit has unity gain and adds +2.5v offset to audio to drive digital attenuator U2 whose input range is 0-5 volts.

Frequency response with C2=0.

Frequency response with C2=1.2nF.

  • 0
    TI__Guru* 76911 points

    Hi Guy,

    Guy Painchaud said:
    With C2=1.2nF, I initially see a cutoff of ~13.1 kHz, but it is not monotonic roll-off.  So other polls and zeros in amp model.  How do I obtain a monotonic roll-off ???

    The best option is to add another roll off near 13.1kHz and this will give what you want. The zero shown in the simulation may be due to LM662A's limited BW, where it runs out of the BW (may be due to parasitic feedforward paths or internal compensation). 

    LMC662A BPF 06172025.TSC

    Alternatively, you may consider MFB bandpass filter, 

    LMC662A MFB 06172025.TSC

    If you have other questions, please let me know. 

    Best,

    Raymond