ADI HMC981

HMC981LP3E is an active bias controller that automatically adjusts the gate voltage of an external amplifer to achieve constant bias current. It can be used to bias any enhancement and depletion type amplifers operating in Class - A regime with Drain voltages from 4V to 12V and drain currents up to 200mA, offering a complete biasing solution. HMC981LP3E achieves excellent bias stability over supply, temperature and process variations, and eliminates the required calibration procedures usually employed to prevent RF performance degradation due to such variations. The HMC981LP3E is housed in an RoHS compliant 3x3 mm QFN leadless package with an exposed backside pad to improve thermal characteristics.

The HMC981LP3E is a fully - integrated Active Bias Controller (ABC) that automatically adjusts the gate voltage of amplifers operating in the Class - A regime. With an internal feedback the automatic gate voltage control achieves constant quiescent bias through the amplifer under bias, independent of temperature and amplifer threshold variations. The quiescent current is adjusted with a resistor connected externally. The HMC981LP3E employs an integrated control circuitry to achieve safe power - up and power - down sequencing of the targeted amplifer. The HMC981LP3E can provide auto - bias solution virtually any amplifer in the market (both enhancement and depletion type) with a quiescent current of up to 200 mA and a supply voltage of up to 12V. The HMC981LP3E has an integrated negative voltage generator to synthesize negative voltages required to drive depletion mode amplifers. If an external negative supply is already available or an enhancement mode device is targeted, the negative voltage generator can be disabled. The HMC981LP3E achieves excellent bias stability over supply and temperature variations with low supply voltage down to 4V. The gate control can both sink and source current (±0.8 mA) to achieve constant bias current over input power variations applied to the amplifer. The HMC981LP3E also generates a second gate voltage (VG2). VG2 can be adjusted through a resistor divider connected to VDD for amplifers which require second gate voltage. The HMC981LP3E ensures the protection of the external amplifer during turn on/off by adjusting the sequence of VDRAIN, VGATE and VG2 outputs. HMC981LP3E controls the bias current of the amplifer under bias with the gate control driver. The current passing through the

• Automatic Gate voltage adjustment (No Calibration required)
• Supply Voltage: 4V to 12V
• Digital Voltage: 3.3V to 5V
• Controls both Enhancement and Depletion type devices
• Adjustable Drain Current up to 200mA
• Sink/Source Gate Current Capability
• Optional Internal negative voltage generation that can be disabled to use external negative rail
• Fast Enable/Disable
• Trigger - out Output for Daisy Chain Power - Up and Power - Down Sequencing
• 16 Lead 3x3 mm SMT Package: 9 mm²

• Microwave Radio & VSAT
• Test Instrumentation
• Fiber Optic Modulator Driver Biasing
• CATV Laser Driver Biasing
• Cellular Base Station
• Wireless Infrastructure Equipment