For price, delivery, and to place orders, please contact Hittite Microwave Corporation:

2 Elizabeth Drive, Chelmsford, MA 01824 Phone: 978-250-3343 Fax: 978-250-3373

Order On-line at www.hittite.com

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HMC981LP3E

v01.0411

ACTIVE BIAS CONTROLLER

Figure 1. Daisy Chain Operation

Operation Modes

HMC981LP3E 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-2. 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 the HMC981LP3E.

The HMC981LP3E 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, HMC981LP3E will stay in standby mode.

Please note that the external negative voltage should be between -2.5V to -3.5V for HMC981LP3E to operate. If your

application requires negative voltages outside this range please contact Hittite application support.

Table 2. 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.2a.

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.2b.

---

FLOAT

GND

N/A

Not allowed. HMC981LP3E 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.2c.

Information furnished by Analog Devices is believed to be accurate and reliable. However, no

responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other

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.

Trademarks and registered trademarks are the property of their respective owners.

For price, delivery, and to place orders: Analog Devices, Inc.,

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

Phone: 781-329-4700 • Order online at www.analog.com

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