6

The RF MOSFET Line

100W, 400MHz, 28V

M/A-COM Products

Released - Rev. 07.07

MRF175LU

• North America Tel: 800.366.2266 / Fax: 978.366.2266

• Europe Tel: 44.1908.574.200 / Fax: 44.1908.574.300

• Asia/Pacific Tel: 81.44.844.8296 / Fax: 81.44.844.8298

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

M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make

changes to the product(s) or information contained herein without notice.

ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions

is considering for development. Performance is based on target specifications, simulated results,

and/or prototype measurements. Commitment to develop is not guaranteed.

PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology

Solutions has under development. Performance is based on engineering tests. Specifications are

typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available.

Commitment to produce in volume is not guaranteed.

MOSFET CAPACITANCES

The physical structure of a MOSFET results in capacitors

between the terminals. The metal oxide gate structure de-

tion of the MOSFET results in a junction capacitance from

data sheets. The relationships between the inter–terminal

capacitances and those given on data sheets are shown

1.

Drain shorted to source and positive voltage at the

gate.

2.

Positive voltage of the drain in respect to source

and zerovolts at the gate. In the latter case the

numbers are lower. However, neither method

represents the actual operating conditions in RF

applications.

measured using method 2 above. It should be noted that-

provided for general information about the device. They are

not RF design parameters and no attempt should be made

to use them as such.

LINEARITY AND GAIN CHARACTERISTICS

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

sented in Figure 3 may give the designer additional infor-

mation on the capabilities of this device. The graph repre-

sents the small signal unity current gain frequency at a

transistors. Since this test is performed at a fast sweep

speed, heating of the device does not occur. Thus, in nor-

mal use, the higher temperatures may degrade these char-

acteristics to some extent.

DRAIN CHARACTERISTICS

One figure of merit for a FET is its static resistance in the

linear region of the output characteristic and is specified un-

der specific test conditions for gate–source voltage and drain

coefficient and constitutes an important design consideration

at high temperatures, because it contributes to the power

dissipation within the device.

GATE CHARACTERISTICS

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

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

resulting in a leakage current of a few nanoamperes. Gate

control is achieved by applying a positive voltage slightly in

Gate Voltage Rating — Never exceed the gate voltage rat-

ing (or any of the maximum ratings on the front page). Ex-

the oxide layer in the gate region.

Gate Termination — The gates of this device are essen-

tially 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.

Using a resistor to keep the gate–to–source impedance low

also helps damp transients and serves another important

function. Voltage transients on the drain can be coupled to

the gate through the parasitic gate–drain capacitance. If the

gate–to–source impedance and the rate of voltage change

on the drain are both high, then the signal coupled to the

gate may be large enough to exceed the gate–threshold

voltage and turn the device on.

HANDLING CONSIDERATIONS

When shipping, the devices should be transported only in

antistatic bags or conductive foam. Upon removal from the

packaging, careful handling procedures should be adhered

to. Those handling the devices should wear grounding

straps and devices not in the antistatic packaging should be

kept in metal tote bins. MOSFETs should be handled by the

case and not by the leads, and when testing the device, all

leads should make good electrical contact before voltage is

applied. As a final note, when placing the FET into the sys-

tem it is designed for, soldering should be done with

grounded equipment.

DESIGN CONSIDERATIONS

The MRF175L is a RF power N–channel enhancement

mode field–effect transistor (FETs) designed for HF, VHF

andUHF power amplifier applications. M/A-COM RF MOS-

FETs feature a vertical structure with a planar design. M/A-

RF POWER MOSFET CONSIDERATIONS