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Data Sheet

ADPA7009-2

BIASING THE ADPA7009-2 WITH THE HMC980LP4E

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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 ADPA7009-2. 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 ADPA7009-2, and the option to use an external negative

voltage source. The HMC980LP4E is also available in die form as

the HMC980-Die.

Figure 68. HMC980LP4E Active Bias Control

APPLICATION CIRCUIT SETUP

Figure 69 shows an application circuit using the HMC980LP4E to

control the ADPA7009-2. When using an external negative supply

for VNEG, see the application circuit shown in Figure 70.

In the application circuit shown in Figure 69, the ADPA7009-2 drain

voltage (VDRAIN) and drain current (IDRAIN) are set by the following

equations:

VDD = VDRAIN + (IDRAIN × 0.85 Ω)

VDD = 5 V + (0.95 A × 0.85 Ω) = 5.81 V

where:

VDD and VDRAIN are in volts.

IDRAIN is in amperes.

R10 = (150 Ω × A) ÷ (IDRAIN)

R10 = (150 Ω × A) ÷ (0.95 A) = 158 Ω

where:

R10 is in ohms.

IDRAIN is in amperes.

LIMITING VGATE FOR THE ADPA7009-2 VGG

ABSOLUTE MAXIMUM RATING REQUIREMENT

When using the HMC980LP4E to control the ADPA7009-2, 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

pin of the ADPA7009-2. 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 Meeting Biasing Requirements of Exter-

nally Biased RF/Microwave Amplifiers with Active Bias Controllers

for more information and calculations for R15 and R16.

The HMC980LP4E application circuits for biasing figures in

the AN-1363 Application Note are two examples of how the

HMC980LP4E is used as an active bias controller. Both application

circuits within the AN-1363 Application Note show the R5 and R7

resistors, which are analogous to the R15 and R16 resistors shown

in Figure 69 and Figure 70.

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