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THS4531: THS4531 as CT amplifier

Ian Benton
Prodigy 170 points
Part Number: THS4531
Other Parts Discussed in Thread: THS4631, OPA810

Tool/software:

Would the THS4531 make a good transresistance amplifier for use with a low current current-transformer (i.e. with less than 10mA output).
I imagine the circuit would have resistors between In+ and Out- and between In- and Out+ and the CT across In+ and In-.

Am I correct in thinking it would deal with the DC offset problems in CT transresistance amplifiers due to the high gain at DC being equal to R divided by the resistance of the CT, as discussed in AD's application note

www.analog.com/.../transimpedance-amplifier-buffers-current-transformer.html

  • 0
    TI__Mastermind 22924 points

    Hello Ian,

    I can certainly help you think through this application.  I would like to confirm you are considering a fully-differential amplifier (FDA), such as the THS4531, which has two outputs as a differential pair.  Is this in line with your application needs?

    One key item for considering FDAs is the relatively low input impedance at VIN+ and VIN-, compared the the high input impedance seen on typical voltage feedback op-amps.  Some voltage-feedback op-amps are even described as high-input impedance, such as ones with a JFET input stage.  Our OPA810 and THS4631 are examples.

    FDAs do allow for shifting the DC common mode voltage to whatever the setting is for the VOCM (output common mode voltage) pin.  Examples are included in the device datasheets.

    Did you have a specific set of requirements or design considerations you wished to work through together?  I can make sure we avoid any common mistakes and select the correct part to solve your signal chain.

    Best,

    Alec