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power amplifier - driving transformer

siauhwa ong
Expert 1510 points
Other Parts Discussed in Thread: OPA561, OPA564

Hi,

I need to drive a custom made transformer ( 1: 1 ratio ) using an amplifier. The transformer impedance is around 6 Ohms. Gain needed is around 1 to 2 only.

The secondary of the transformer is connected to a 5 Ohms load.  Output voltage is around 5Vpp.

Any reference design for that requirement ?

And, by the way, what's the advantages and disadvantages of using differential output and single ended output for driving the transformer.

Thank you

  • 0
    TI__Guru* 93105 points

    Hi Siauhwa,

    A power operational amplifier should be able to drive a 5 Ohm load through a 1:1 transformer. Power operational amplifiers are similar to conventional, lower power ones except that the are capable of providing hundreds of milliamperes, or amperes, of output current.

    Two power operational amplifiers to consider are the OPA561 and OPA564. They have output current capabilities of 1.2 Amps and 2.0 Amps, respectively. They have a wide gain bandwidth of 17 MHz and operate 7 to 16 V, and 7 to 26 V, respectively. They are often used as the power amplifier in power line communications (PLC) applications where they drive a step-up transformer. You can see such applications in their data sheet accessible through their web pages:

    http://www.ti.com/product/opa561

    http://www.ti.com/product/opa564

    The PLC application has very rigorous electrical overstress (EOS) survivability requirements and the schematics include numerous protection devices. Most of them would not be required in other applications.

    The main advantage of a differential-out amplifier is twice the output swing, and twice the effective slew rate when compared to a single-ended output operational amplifier having the same electrical specifications. Very often two power operational amplifiers are connected in the bridged-T configuration to accomplish the equivalent of a differential output amplifier. The transformer's primary winding is connected between the two outputs of a bridged-T connected amplifiers while the load connected directly to the transformer's secondary winding.

    Regards, Thomas

    PA - Linear Applications Engineering