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HMC920LP5E

v07.1013

ACTIVE BIAS CONTROLLER

Operation Modes

HMC920LP5E can be configured to bias both enhancement and depletion mode external amplifiers. The mode of

operation can be selected by setting two pins (VNEGFB, VGATEFB) as tabulated in Table-1. The connection to the

VNEGIN should be adjusted accordingly.

In order not to bias external amplifier in a wrong region, please make sure that the correct mode of operation is

selected before powering up HMC920LP5E.

HMC920LP5E does not allow the internal negative voltage generator to work if an enhancement mode is selected.

Therefore, if VNEGFB is left floating while VGATEFB is grounded, HMC920LP5E will stay in standby mode.

Please note that the external negative voltage should be between -2.5V to -3.5V for HMC920LP5E to operate.

Table 1. Mode Selection

VNEGFB

VGATEFB

VNEGIN

Description

MODE1

(Depletion/Master Mode)

FLOAT

FLOAT

Connected to

VNEGOUT

Depletion mode transistor. Internal negative voltage generator is

active and generates -2.5V. Sample application schematic given

shown in Fig.4a.

MODE2

(Depletion/Slave Mode)

GND

FLOAT

Connected to

External VSS

Depletion mode transistor. Internal negative voltage generator is

disabled. An external negative voltage less than -2.3V should be

connected to VNEGIN. Sample application schematic given shown

in Fig.4b.

---

FLOAT

GND

N/A

Not allowed. HMC920LP5E stays in standby.

MODE3

(Enhancement Mode)

GND

GND

Connected to

GND

Enhancement mode transistor. Internal negative voltage generator is

disabled. Sample application schematic given shown in Fig.5.

Figure 3. Daisy Chain Operation

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rights of third parties that may result from its use. Specifications subject to change without notice. No

license is granted by implication or otherwise under any patent or patent rights of Analog Devices.

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One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106

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Application Support: Phone: 1-800-ANALOG-D