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INA128: high voltage differential input (60V) conversion to single ended

Christophe TANNEAU
Prodigy 30 points
Part Number: INA128
Other Parts Discussed in Thread: INA146

I would like to convert a 60 input  voltage (differential) to a single ended one, with output voltage approx 5V. My power supply is 24 volts. Which opam can you recommend to withstand 60V. I can cascade several of them for instance one for each entry

Regards

  • 0
    TI__Mastermind 23050 points

    Hi Christophe,

    The INA146 should work well for your application. It has internal precision trimmed resistors set to a gain of 0.1. This will take your signal down to 6V. From there you can attach a 50kOhm resistor from pin 8 to ground to create a voltage divider with R5 (see diagram below) to produce your 5V output. Alternatively, if you need greater precision you could use the second internal op-amp as a buffer and make a voltage divider on the output with 0.1% resistors. 

    Regards,

    Zak Kaye

    Precision Amplifiers Applications

  • 0 in reply to Zak Kaye
    Prodigy 30 points

    But what about Vo output reference. I have a 0-24V power supply (non symetrical) . can I reference RG1 to the V- and V- = gnd ?

  • 0 in reply to Christophe TANNEAU
    TI__Mastermind 23050 points

    Thank you for clarifying your supply. You would only use RG1 if you were trying to add gain to the signal, but since you are trying to stay below 5V there would be no reason to populate this component. That is why I recommended configuring A2 as a buffer. Its output will be set by the resistor you put on pin 8. It's okay that you are using asymmetric supplies as long as your desired output signal is within the range of your supplies. Please be aware though that with the negative supply grounded, you will see some non-linearity in the output signal around 100mV since this is the closest the output can swing to the rail. Furthermore, the output of A1 is still going to be a bipolar signal, so if you want an output signal between 0 to 5V, you will need a reference voltage to add a DC offset. In this case you would need a 3V reference on the Ref pin. I have attached a TINA simulation file for the configuration I have described. 6138.INA146 High voltage input to single ended.TSC

    Regards,

    Zak Kaye

    Precision Amplifiers Applications