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THS3491: THS3491 application question and roadmap question

Dane Zhang
Expert 4095 points
Part Number: THS3491
Other Parts Discussed in Thread: OPA817, , OPA810

Hi team,

we want to develop a 1000:1 high-voltage differential probe for the detection of high-voltage pulse signals. The maximum input is ±7kV, corresponding to the maximum output ±7V, and the signal bandwidth is more than 100MHz. The circuit topology is as shown below:

Now U1/U2 is ready to use OPA817 with high input impedance. Since OPA817 can only output about 3.5V, it cannot be used on U3. You need to find an op amp with an output greater than ±7V and a large and small signal bandwidth >100MHz. Please provide some selection and design suggestions.
Now I have initially found a THS3491. The large signal bandwidth meets the requirements according to the parameters in the specification. However, whether small signals below 100mV are OK is not clear from the specification. Please help confirm or recommend a more suitable model.

  • 0
    TI__Expert 8650 points

    Hi Dane,

    I was curious if the customer had any additional information on the signal they are trying to amplify such as a slew rate as well as how large of an output signal is expected, as this will help narrow down an amplifier. However, the THS3491 should not have a problem with signals in the 100mVpp range and does have the required bandwidth. One concern is the large resistor values at the input, there is a concern that this input network could interact with the input capacitance of the OPA810 and potentially impact the bandwidth of the circuit. Has the customer tested this configuration? 

    Best regards,

    Ignacio