HMC920 Active Bias Controller

BradtheRad said:

Perhaps this method might be adapted to your project. Biasing arrangement discourages thermal runaway (schematic I found in a book).

If the transistor conducts too much, then the voltage at the collector goes down, automatically easing up on bias current, in turn reducing how much the transistor conducts.

View attachment 167512

Click to expand...

vfone said:

Seems that HMC920 has just an LDO to generate the drain current. Is not showing any current sensing circuit to adapt dynamically the drain current. It has only a current sensing for short-circuit protection.
As is mentioned at page 11 there is a possibility to adjust the drain current using an external resistor (R4).
Thus, a complex schematic would require a drain current sensing circuit, which adjust somehow the variable resistor R4 and so, the drain current.

Click to expand...

vfone said:

Seems that HMC920 has just an LDO to generate the drain current. Is not showing any current sensing circuit to adapt dynamically the drain current. It has only a current sensing for short-circuit protection.
As is mentioned at page 11 there is a possibility to adjust the drain current using an external resistor (R4).
Thus, a complex schematic would require a drain current sensing circuit, which adjust somehow the variable resistor R4 and so, the drain current.

Click to expand...

vfone said:

Seems that HMC920 has just an LDO to generate the drain current. Is not showing any current sensing circuit to adapt dynamically the drain current. It has only a current sensing for short-circuit protection.
As is mentioned at page 11 there is a possibility to adjust the drain current using an external resistor (R4).
Thus, a complex schematic would require a drain current sensing circuit, which adjust somehow the variable resistor R4 and so, the drain current.

Click to expand...