MRF140 View Datasheet(PDF) - M/A-COM Technology Solutions, Inc.

Part Name

Description

Manufacturer

MRF140

The RF MOSFET Line 150W, to 150MHz, 28V

M/A-COM Technology Solutions, Inc. 

MRF140

The RF MOSFET Line

150W, to 150MHz, 28V

Rev. V1

RF POWER MOSFET CONSIDERATIONS

MOSFET CAPACITANCES

The physical structure of a MOSFET results in capaci-

tors between the terminals. The metal oxide gate struc-

ture determines the capacitors from gate–to–drain (Cgd),

and gate–to–source (Cgs). The PN junction formed dur-

ing the fabrication of the RF MOSFET results in a junc-

tion capacitance from drain–to–source (Cds).

These capacitances are characterized as input (Ciss),

output (Coss) and reverse transfer (Crss) capacitances

on data sheets. The relationships between the inter–

terminal capacitances and those given on data sheets

are shown below. The

Ciss can be specified in two ways:

1. Drain shorted to source and positive voltage at the

gate.

2. Positive voltage of the drain in respect to source

and zero volts at the gate. In the latter case the

numbers are lower. However, neither method repre-

sents the actual operating conditions in RF applica-

GATE CHARACTERISTICS

The gate of the RF MOSFET is a polysilicon material, and

is electrically isolated from the source by a layer of oxide.

The input resistance is very high — on the order of 109

ohms

— resulting in a leakage current of a few nanoamperes.

Gate control is achieved by applying a positive voltage

slightly in excess of the gate–to–source threshold voltage,

VGS(th).

Gate Voltage Rating — Never exceed the gate voltage

rating. Exceeding the rated VGS can result in permanent

damage to the oxide layer in the gate region.

Gate Termination — The gates of these devices are es-

sentially capacitors. Circuits that leave the gate open–

circuited or floating should be avoided. These conditions

can result in turn–on of the devices due to voltage build–up

on the input capacitor due to leakage currents or pickup.

Gate Protection — These devices do not have an internal

monolithic zener diode from gate–to–source. If gate protec-

tion is required, an external zener diode is recommended.

tions.

LINEARITY AND GAIN CHARACTERISTICS

In addition to the typical IMD and power gain data pre-

sented, Figure 5 may give the designer additional infor-

mation on the capabilities of this device. The graph

represents the small signal unity current gain frequency

at a given drain current level. This is equivalent to fT for

bipolar transistors. Since this test is performed at a fast

sweep speed, heating of the device does not occur.

Thus, in normal use, the higher temperatures may de-

grade these characteristics to some extent.

9

M/A-COM Technology Solutions Inc. (MACOM) and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice.

Visit www.macom.com for additional data sheets and product information.

For further information and support please visit:

https://www.macom.com/support

Share Link: