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TLV8802: Unity gain bandwidth

Niclas Samuelsson
Intellectual 490 points
Part Number: TLV8802

Hello! I am planning on using the TLV8802 in a 2-stage amplification circuit, very much like the circuit in the picture below, 

I am not very knowledgeable of OP amps. The Unity Gain Bandwidth is 6kHz. Both filter stages (Stage 1 and Stage 2 above) have lower and upper limits at approximately 0.8Hz and 1.2Hz (so, not exactly like the picture above). Does that mean that I should divide 6kHz by the gains I have in my bandpass interval (around 1Hz) to get the bandwidth? Or should I divide 6kHz by the DC gains? I.e ignoring the capacitances in the gain circuits and just using the resistors. 

Since I have bandpass filters from 0.8Hz to 1.2Hz, how close to to 1.2Hz can I reasonably go? How much margin is generally recommended in the bandwitdh? 10Hz? 30Hz? 100Hz?

  • 0
    TI__Mastermind 19257 points

    Hey Niclas, 

    I recommend viewing this TIPL video for more information on bandwidth calculations: 

    For a quick answer to your question, you would divide the UGBW (6 kHz) with the DC gain of that stage (just the resistors). 
    This design guide for a similar circuit to the one you have pictured goes into detail on the calculations of your bandwidth, low/high frequency cutoff: 

    In that example, the designer allows ~20Hz of margin between their bandpass of (0.7 to 10Hz) and the bandwidth per stage of 36 Hz. 
    I recommend starting around there and determining what is best for your design through testing. 

    All the best,
    Carolina