HMC920 Active Bias Controller

[Atif Hussain Shah]

My Amplifier CHA3024 changes its gain as temperature changes. I want to use HMC920 Active bias Controller for maintaining its drain current constant and for sequencing of Amplifier.
But i am not sure that will this active Bias Controller be able to maintain constant gain by monitoring drain current(maintaining fixed Bias point) and mitigate the effects on gain due to temperature changes?

 

[vfone]

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.

 

[BradtheRad]

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.

 

[Atif Hussain Shah]

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

Thanks for help.

--- Updated Feb 15, 2021 ---

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.

thanks for help

--- Updated Feb 15, 2021 ---

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.

HMC980 is from same family. I think these lines which i highlighted, shows that it controls drain current continuously by adjusting Vgate voltage.

 

[vfone]

HMC920 has also the possibility to adjust automatically the gate bias of the external amplifier.

 

[biff44]

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.

try increasing the voltage headroom on the chip