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OPA3695: Gain and cutoff frequency

ATHIRA K VINOD
Prodigy 70 points
Part Number: OPA3695


Tool/software:

Dear Team,

I am designing a signal conditioning circuit for offset and gain adjustments referring to TI's doc . I have to amplify my sine wave from ±0.5V to 0 -3.3V. the signal frequency maximum is 100MHz. I selected OPA3695 op-amp.

While doing simulations, for a gain of 3.3 I am getting a bandwidth of 30MHz only. The gain reduces after 10MHz. The datasheet shows that 450MHz bandwidth for gain of 8. What could be the reason. I am attaching the relevant circuits and waveforms.

Please do the needful

  • +1
    TI__Genius 17775 points

    Hi,

    The reason you are seeing reduced bandwidth performance is because the Rf resistor being implemented. This device is a current feedback device, and its bandwidth performance is strongly dependent on the choice of Rf. For every current feedback device, we include data for different Rf values that were tested as well as recommended values to use for a specific gain. Choosing to high of a value will reduce your bandwidth, and choosing to low of a value will result in the circuit being unstable. Table 2 in the datasheet highlights which resistor values should be used. For a gain of 3.3V/V, an RF value of around ~550ohms should result in better performance.

    Best Regards,

    Ignacio