MMZ09332BT1 bias control

[SimMG]

We are currently using the MMZ09332BT1 as a PA stage on an SDR based transceiver.

In the datasheet for it one of the features touted is "Active Bias Control (adjustable externally)" does this mean that linearity can be sacrificed for a lower quiescent/operational current draw? If yes, are there any graphs/tables of bias resistor values vs expected performance? if the answer is "NO" bias control is not for power saving, then what is the function of this externally adjustable active bias?

Thank you

Simon

[ErikaC]

Hello,

MMZ09332BT1 is bipolar transistor Technology (InGaP HBT) amplifier. Transistor bias is defined by current rather than voltage. The amplifier provides active bias control circuit the same as shown in Figure 5 of the following application note:

https://www.nxp.com/files/rf_if/doc/app_note/AN3100.pdf

The bias points for the first and second stages of amplifier are defined by external resistors at VBA1 and VBA2 pins.

It is not reasonable to use this device as as variable gain amplifier. The signal gain of the amplifier slightly depends on the bias. The bias rather defines power range and operating point (class A or AB).

I see the only valuable reason to change biasing to reduce power consumption if less maximum power is required.

PS. Since we do not consider bias as a controlled value, all the specs are provided at fixed bias parameters.

[SimMG]

Thank you, so it is as i have surmised, that power saving at the expense of performance is possible by reduction of bias in the device.

However, I have looked at the application note you mention (Rev 3), and for the MMZ09332B, with external bias control resistors it would indicate that bias control is via a current mirror, as defined in Fig 5 of the AN. in the section relevant to this figure it says that the datasheet for a device will define the Vref setpoint for the current mirror for optimal operation, but the datasheet for the MMZ09332B , which is still at Rev 0, has no mention of this defined Vref.

Regards

Simon