AnsweredAssumed Answered

Need OP amp recommendation

Question asked by SMcBride Employee on Mar 17, 2015
Latest reply on Mar 31, 2015 by SMcBride

Hello EZ,


I support a customer who's using the HMC6981LS6 power amplifier:


Hittite Microwave - HMC6981LS6, Linear & Power


This power amp has an integrated power detector diode (Vdet pin), plus a reference diode (Vref pin) for temperature compensation.

The customer would use these two diodes by taking the difference in their output voltages (Vref-Vdet) as being indicative of the amp's RF Pout.

Depending upon the RF Pout, the voltages output from these pins would be as follows:


Vref: 0 V through 1 V, approx., as measured open circuit

Vdet -2 V through 1 V, approx., as measured open circuit


The data sheet suggests an amp application circuit for applying DC bias to the two diodes (via 100k ohm series resistors) and for using an OP amp to take the difference between the two diodes' output voltages.

However, the data sheet does not suggest a particular OP amp, so the customer has requested assistance in selecting one.

Attached are images excerpted from the data sheet showing the application circuit, the detector pin descriptions, and a plot of the (Vref-Vdet) vs. RF Pout curve.


Would you please help recommend an ADI OP amp that would be suitable for this application?

I will direct the customer to this thread so that they may provide additional details regarding their requirements.