1 watt, 5 volts, 400 kHz

Those specs are so easy that it would be cheap and simple to bang together a simple one transistor Class A amplifier using a big friendly power mosfet transistor. Use one pot for DC bias, another for gain. "Rat's Nest" direct wiring (no PCB).

The L272 DUAL POWER OPERATIONAL AMPLIFIER has two channels and can deliver the power you need if you use both cahannels. Gain-BW is 350 kHz for one of them, so you may be into roll-off, but there's usually a margin and with two of them, you should be OK.

The class A version, that IR mentions, may be difficult to make behave properly with the inductive load that you seem to have.

If you want a solution with no fuzz and a reserve for future use, I can highly recommend the Rigol 1022 function/arbitrary generator with the 10 W add-on power amplifier. Very good value for money.

Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.

Sorry - VE1BLL.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

If the "coil transformer" is being employed, or tested, as a transformer rather than as a coil (inductor, reactive load), then it may well be a reasonably flat load. But, yes, well worth checking.