FAQ: Powering op-amps (or ADCs) with Dual Supplies

    Q.

    How do I power op-amps (or ADCs) with Dual Supplies?

     

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    A.

    Powering op-amps (or ADCs) with dual supplies is a common requirement. There are multiple ways of solving this problem depending on what voltages are already available to you.

     

    For example, if you have a positive voltage and need to generate a negative one a Cuk topology (like the one you found with the ADP1621) is an option. The same can be implemented with a ADP1613 requiring less components, although a cuk topology typically needs more components it is the least noisy option unless you want to follow it with a negative LDO.

     

    Another handy topology is the inverting buck boost. This can be implemented with a buck regulator such as the ADP2300 (or many other more integrated parts). Here is AN-1083 describing how to do it.

     

    Powering op-amps often leads to the need of a positive and a negative rail that are equal in voltage but of reversed polarity. In this case a coupled Sepic-Cuk could be handy, especially because the op-amp current requirements are balanced between the positive and negative rail.

     

    This topology is covered as part of the ADIsimPower tool set by downloading one of the SEPIC_Cuk tool.

    Here is the link for the ADP1613 tool.

    http://download.analog.com/PMP/ADP161x_SEPIC_Cuk_Designer.zip

     

    Another option is to start with an inverting charge pump such as the ADM8860 or ADP3506 followed by either a negative LDO or a LC filter.

     

    In power the options are many and often are dictated by what's already available on the board or what else you are trying to power.

     

    AnalogXPRT

     

    This FAQ was generated from the following discussion: low negative voltage PSU for precision ADC