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Phone: 978-250-3343

Fax: 978-250-3373

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Application Support: Phone: 978-250-3343 or apps@hittite.com

16

HMC980

v00.0312

Active BiAs controller

High current

Figure 2. Daisy Chain Operation

operation Modes

hMC980 can be configured to bias both enhancement and depletion mode external amplifiers. the mode of operation

can be selected by setting two pads (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 hMC980.

the hMC980 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, hMC980 will stay in standby mode.

please note that in depletion slave mode the external negative voltage should be between -2.3V to -3.5V for hMC980

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.3a.

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.3b.

---

Float

GnD

n/a

not allowed. hMC980 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.3c.