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Data Sheet

ADPA7009CHIP

Rev. 0 | Page 21 of 28

BIASING THE ADPA7009CHIP WITH THE HMC980LP4E

The HMC980LP4E is an active bias controller that is designed

to meet the bias requirements for enhancement mode and

depletion mode amplifiers such as the ADPA7009CHIP.

The controller provides constant drain current biasing over

temperature and device to device variation, and properly

sequences gate and drain voltages to ensure the safe operation of

the amplifier. The HMC980LP4E also offers self-protection in

the event of a short circuit, an internal charge pump that

generates the negative voltage needed on the gate of the

ADPA7008CHIP, and the option to use an external negative

voltage source. The HMC980LP4E is also available in die form

as the HMC980-Die.

VDD

ALM

VG2_CONT

14 VG2

15 VNEG

16 VGATE

17 VDRAIN

18 VDRAIN

HMC980LP4E

CONTROL

BLOCK

GATE

CONTROL

–

BAND GAP

NEGATIVE

VOLTAGE

GENERATOR

PACKAGE

BASE

GND

Figure 68. HMC980LP4E Active Bias Control

APPLICATION CIRCUIT SETUP

Figure 69 shows an application circuit using the HMC980LP4E

to control the ADPA7009CHIP. When using an external

negative supply for VNEG, refer to the application circuit

shown in Figure 70.

In the application circuit shown in Figure 69, the

ADPA7009CHIP drain voltage, VDRAIN, and drain current,

IDRAIN, are set by the following equations:

VDD = VDRAIN + (IDRAIN × 0.85 Ω)

(1)

VDD = 5 V + (0.85 A × 0.85 Ω) = 5.72 V

where:

VDD and VDRAIN are in volts.

IDRAIN is in amperes.

R10 = (150 Ω × A) ÷ (IDRAIN)

(2)

R10 = (150 Ω × A) ÷ (0.85 A) = 176 Ω

where:

R10 is in ohms.

IDRAIN is in amperes.

LIMITING VGATE FOR THE ADPA7009CHIP VGGx

ABSOLUTE MAXIMUM RATING REQUIREMENT

When using the HMC980LP4E to control the ADPA7009CHIP,

the minimum voltages for VNEG and VGATE must be −1.5 V

to keep the voltages within the absolute maximum rating limit

for the VGGx pad of the ADPA7009CHIP. To set the minimum

voltages, set R15 and R16 to the values shown in Figure 69 and

Figure 70. Refer to the AN-1363 Application Note for more

information and calculations for R15 and R16.

The HMC980LP4E application circuits for biasing figures in

the AN-1363 are two examples of how the HMC980LP4E is

used as an active bias controller. Both application circuits

within the AN-1363 show the R5 and R7 resistors, which are

analogous to the R15 and R16 resistor shown in Figure 69 and

Figure 70.

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