choke(mmic)
Is it all the MMIC power amplifier integrated the RF choke inside? Does it also include some bias resistors also? Is the datasheet drain bias voltage directly apply to the transistor drain, or just a portion of it applied to the transistor drain?
And also, is it in most of the datasheet, the drain bias voltage and drain current are corresponding to the quiescent point (DC bias point)? When the PA is working nearly the saturation, what will be the peak voltage and current that we can observe from the device? Is it twice of the quiescent value?
Thanks.
Is it all the MMIC power amplifier integrated the RF choke inside? Does it also include some bias resistors also?
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some of them include the RF choke on chip, but some not, because of the large value of RF choke. MOst bias resistors are on chip.
Drain bias usually apply to the drain via a RF choke!
Thanks, wireless man.
But I check many MMIC amplifier recommended layout, they all put the 100pF by-pass capacitors right next to the power supply pin of the MMIC (I suppose that is for drain bias). So in this case, I thought the RF choke is already integrated. Otherwise, I think the by-pass capacitors just act as GND at the drain, and get all the RF signals short the GND.
Please correct me if my understanding is not correct.
yes, the by-pass capacitor usually consists of 10 pF, 100 pF, 1000 pF in parallel, to short the RF signal leaked from RF choke.
Most of the MMIC power amplifiers operates in Class AB, so the saturation current is few times greater than quiescent current.
The drain bias voltage goes direct to the drain through the choke. Generally there is no resistor added in series with the choke, because this will decrease the efficiency.
Some manufacturers uses as a choke, for high frequency MMICs (fo>1700MHz), pieces of internal bond wires (inside of the package, between die and pins). The inductance of these bond wires is very predictable, having also low DC resistance.