ADL8106ACEZ-R7 datasheet(24/26 Pages) AD

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Data Sheet

ADL8106

APPLICATIONS INFORMATION

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Rev. B | 24 of 26

Figure 89. Active Bias Control of the ADL8106 Using the HMC920

HMC920 Bias Sequence

When the ADL8106 bias control circuit (HMC920) is set up, the bias

can be toggled on and off by applying 3.5 V (high) or 0 V (low) to

the EN pin. If EN is left floating, the pin floats high. When EN is

set to 3.5 V, the gate voltage (VGATE) initially drops to −2 V and the

drain voltage (VDRAIN) rises to +3 V. Then, VGATE and the VGG1

voltage (VGG1) increase until the drain current (IDRAIN) reaches its

target value. The closed control loop then regulates IDRAIN to its

target value. When the EN pin goes low, VGATE and VGG1 drop back

to −2 V, and VDRAIN drops to 0 V.

Constant Drain Current Biasing vs. Constant

Gate Voltage Biasing

In comparison to a constant gate voltage bias, where the current

increases dynamically when RF power is applied, constant drain

current bias results in constant power consumption.

The performance of the constant drain current circuit is summarized

in Figure 90 to Figure 95. These figures include comparisons with

constant gate voltage bias.

The OP1dB and PSAT performance for the constant drain current

bias can be varied by varying the drain current setpoint. By increas-

ing the bias current, OP1dB and PSAT improve as shown in Figure

92 and Figure 95. The trade-off with constant drain current is that

the drain current is present for all RF input and output power levels.

Note that Figure 90 indicates a current consumption of 175 mA,

which includes the complete current consumption of the circuit, that

is, 140 mA drain current for the ADL8106 and an additional 35 mA

of IDQ in the HMC920. Also, the PAE for constant drain current bias

in Figure 93 assumes a supply voltage of 5 V (the supply voltage to

the HMC920) and a constant current of 175 mA.

Figure 90. IDD vs. PIN, VDD = 3 V, Frequency = 36 GHz, Constant Drain Current

Bias (140 mA + 35 mA) and Constant Gate Voltage Bias (IDQ = 120 mA)

Figure 91. OP1dB vs. Frequency for Various Temperatures, Data Measured

with Constant Drain Current of 140 mA

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