ADPA7007AEHZ-R7 datasheet(18/23 Pages) AD

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ADPA7007

Data Sheet

Rev. 0 | Page 18 of 23

BIASING ADPA7007 WITH THE HMC980LP4E

The HMC980LP4E is an active bias controller that measures

and regulates drain current by automatically adjusting the gate

voltage. The HMC980LP4E can control the biasing of RF

amplifiers with drain voltages up to 16.5 V and currents up to

1.6 A. 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 offers self protection in the event of a short

circuit, as well as an internal charge pump that generates the

negative voltage required on the gate of the ADPA7007. The

HMC980LP4E also provides the option to use an external

negative voltage source. The HMC980LP4E is also available in

die form as the HMC980.

APPLICATION CIRCUIT SETUP

Figure 56 shows a schematic of an application circuit using the

two HMC980LP4E devices to control the ADPA7007. When

using an external negative supply for VNEG, refer to the

schematic in Figure 57.

Although the ADPA7007 is specified with a quiescent drain

current of 1400 mA, the operational drain current, IDRAIN, required

to achieve the maximum output power from the ADPA7007

must be set closer to 1800 mA. The IDRAIN current increases to

approximately 1800 mA when the RF input power is 15 dBm,

the approximate input compression point (see Figure 41). As a

result, a target IDRAIN of 1800 mA is chosen.

Two HMC980LP4E devices are needed to support current

levels at 1800 mA because a single HMC980LP4E device can

support a maximum current of 1600 mA. In the application

circuit shown in Figure 56 and Figure 57, the ADPA7007 drain

voltage and drain current are set by the following equations:

VDRAIN = VDD − IDRAIN × 0.85 Ω

(1)

where:

VDRAIN = 5 V, the drain voltage from Pin 17 and Pin 18 of the

HMC980LP4E.

VDD = 5.765 V, the supply voltage to the HMC980LP4E.

IDRAIN = 1800 mA, the constant drain current from Pin 17 and

Pin 18 on the HMC980LP4E.

150

DRAIN

R10

Ω

(2)

where:

IDRAIN = 900 mA (for each HMC980LP4E, per the dual bias

setup in Figure 56).

R10 = 166.66 Ω.

LIMITING VGATE AND VNEG FOR ADPA7007 VGGX

ABSOLUTE MAXIMUM RATING REQUIREMENT

When using the HMC980LP4E to control the ADPA7007, set

the minimum voltages for the VNEG and VGATE pins of the

HMC980LP4E to −1.5 V to keep these voltages within the absolute

maximum rating limits for the VGGx pins of the ADPA7007. To

set the minimum voltages, use the R15 and R16 resistors shown

in Figure 56 and Figure 57. Refer to the AN-1363 Application

Note, Meeting Biasing Requirements of Externally Biased

RF/Microwave Amplifiers with Active Bias Controllers, for more

information and calculations for R15 and R16.

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