Rf Mosfet Driver Ic

January 2003 SWITCH MODE POWER SUPPLIES RF GENERATORS MOSFET DRIVER IC S These ultra-fast high current drivers are optimized to drive IXYS RF MOSFETs.

DEIC421 RF MOSFET DRIVER 20 Ampere Ultrafast RF MOSFET Driver With Kelvin Connection Figure 1 - DEIC421 Functional Diagram Applications Driving RF MOSFETs.

DVRFD630-631 MOSFET Driver Development Board

The DVRFD630 and DVRFD631 development boards are a general purpose circuit board designed to simplify the evaluation of the IXRFD630 and IXRFD631 MOSFET gate drivers and provide a building block for power circuit development. The IXRFD630 or IXRFD631 gate driver is factory installed on the evaluation board and is fully tested.

Two board configurations are available for each driver: The EVRFD63x 150/275 configuration enables the user to drive DE150 or DE275 sized DE Series MOSFETs, while the second EVRFD63x 375/475 configuration has a larger footprint pad for DE375 or DE475 sized DE Series devices. The board design allows both the driver and MOSFET to be attached to a heat sink, and in doing so allows the board assembly to be used as a ground referenced, low-side power switch.

Optimized circuit layout to assist users with their own designs

Add any one of four IXYSRF package sizes

Demonstrate operation of IXYSRF gate drivers and MOSFETs.

Stand-alone operation as a low side ground reference power switch when a MOSFET is added.

IXRFD630 Gate Driver, accommodates DE150 or DE275 series MOSFETs

IXRFD631 Gate Driver, accommodates DE150 or DE275 series MOSFETs

IXRFD630 Gate Driver, accommodates DE375 or DE475 series MOSFETs

IXRFD631 Gate Driver, accommodates DE375 or DE475 series MOSFETs

ComponentsMOSFETs, Drivers, Diodes Power ModulesEvaluation BoardsDVRFD630-631 MOSFET Driver Development Board

DVRFM631 Combination MOSFET and Gate Driver Development Board Data Sheet

The DVRFM631DF18N50 and DVRFM631DF12N100 development boards are general purpose circuit boards designed to simplify the evaluation of the IXZ631DF18N50 500V 18A and  IXZ631DF12N100 1000V 12A combination gate driver and MOSFET RF power modules, and to provide a building block for power circuit development.

While the circuit board is the same, either a 500 V DVRFM631DF18N50 or 1000 V DVRFM631DF12N100 module is available and is factory installed and fully tested. The board design allows the module to be mounted to a heat sink, and in doing so allows the board assembly to be used as a ground referenced, low-side power switch

Optimized layout to assist users with their own designs

Demonstrate operation of IXYSRF power modules

Low-side ground referenced power switch

DVRFM631DF18N50: 500 V 18A configuration with IXZ631DF18N50 device.

DVRFM631DF12N100: 1000 V 12A configuration with IXZ631DF12N100 device.

The IXZ631DF18N50 module combines the IXRFD631 gate driver with a 500 V, 18 A power RF MOSFET in a single device to enable more compact and efficient designs in Class D, E, HF, and RF applications along with a reduced parts count.

The IXZ631DF12N100 module combines the IXRFD631 gate driver with a 1000 V, 12 A power RF MOSFET in a single device to enable more compact and efficient designs in Class D, E, HF, and RF applications along with a reduced parts count.

Designed for evaluation purposes, the PRF-1150 provides a reference for utilizing IXYSRF MOSFETs and driver in a Class E generator application producing 1kW of RF power in the ISM band at 13.56MHz.

The compact, self-contained layout only requires an external power supply, 50 ohm load, and cooling fan for high efficiency, 1kW operation. The PRF-1150 operation and design is also detailed in an application note, located on the IXYSRF web page, that provides additional design information concerning the Class E topology, IXYSRF components, and to help users create their own class E generators.

DEIC420 RF MOSFET Gate Driver IC datasheet, cross reference, circuit and application notes in pdf format.

Analog Devices MOSFET driver family provides high speed, high current MOSFET drive capability for efficient switching conversion in ac-to-dc and isolated dc-to-dc.

Robust MOSFET driver for RF, class-D inverters datasheet, cross reference, circuit and application notes in pdf format.

24 MOSFET RF Amplifier - Step by Step. Gate Drive and Drivers. Driver IC s connected to, and driving the gate s.

Selecting a driver for the gates of the final RF amplifier is probably

the most important design aspect of a class E transmitter. Much work has

been done in this area. More than any other part of the transmitter, the

driver will determine the stability and to some extent, the efficiency

of the RF amplifier. Some types of drivers include:

Direct, sine wave drive of the gates from an external transmitter, transformer coupled

Sine wave drive using a smaller, internal class E stage, transformer coupled

Descrete component square wave digital, non-resonant driver connected directly to the gates or through a transformer

Driver IC s connected to, and driving the gate s

The main function of the driver is to supply the RF gate voltage to the

final RF MOSFETs. A second, very important function of the driver is to

hold the gates in either the on state, or off state, and not allow the gates

to float under any conditions. If the gates float, parasitics are likely

The RF gate voltage should be around 24 to 30 volts Peak to Peak

assuming sine wave drive, or alternatively, about 12 volts Positive

This drive level must be maintained during all phases of

modulation. A poor driver will result in poor performance. Remember,

all the gate drive power is converted to heat within the MOSFET. This

factor must be considered with figuring device dissipation, and heat

Digital gate drive is the best way to drive the gates of MOSEFTs used in

class E amplifiers. There are several advantages to digital gate drive:

Broadband - no tuning is required, even when changing bands.

More Efficient - only positive voltage is supplied to the gates, so less heat is generated.

The gates are held is the on state or the off state. This significantly reduces the chances of parasitic oscillations.

Easier construction than analog transformer coupled drive systems.

Phase shift within the driver circuitry can be eliminated, or alternatively, carefully controlled and adjusted.

The waveform above shows the output of an IXDD414 driver driving 2 FQA11N90

gates. This is a good gate waveform, with no ringing or other anomalies present.

A driver which delivers only a positive peak

to the MOSFET gates is more efficient than a sine wave driver. This is

because the only useful part of the driving cycle is the positive peak.

The negative peak does not contribute in any way to driving the MOSFET,

however the energy contained in the negative cycle is still converted

to heat within the MOSFET gates.

The gates of the MOSFETs are big capacitors. Keep the leads from the

drive ICs to the gates SHORT within reason. The gates represent a low impedance at RF. They

can be driven at RF, but you must take care to keep the leads as short

as possible. When paralleling MOSFETs be sure to keep the gate leads

REALLY SHORT, and keep the MOSFETs fairly close together to ensure that

all the MOSFETs are being driven with the same gate voltage, and all

Although digital gate drive is generally simpler to implement, and will usually

yield better results, there are still many applications where analog sine wave

gate drive is desired or mandated.

With analog drive, a driver transformer or transformers are usually used to

couple the driver to the gates. A step down ratio is generally employed

to help match the driver to the very low gate impedance. The MOSFET gates

are often connected in parallal, and a wide gate bus, constructed from

copper or brass strap is used.

can be an external transmitter, or can be built into the overall system in

Since the gates of MOSFETs represent SO much capacitance, it is

important to remember that even a relatively short piece of wire or

copper strap will represent sufficient inductance, and can cause an RF phase

shift to occur along the copper strap. If you have a number of MOSFET

gates in parallel along a piece of copper strapping, you need to ensure

that the same amount of drive, in the same phase, is delivered to each

device. The gate bus should be quite wide up to 1 inch to reduce stray

On 75 meters using analog sine wave drive, a 10 MOSFET transmitter will require approximately

20-30 watts of power delivered to the gates. Figure about twice this

amount on 40 meters. The important thing to ensure is that you have at

least 12V 24v peak to peak at the gates of the MOSFETs.

With digital gate drive, figure approximately. 5A to. 8A at 12VDC driver power

per MOSFET on the 75 meter band.

Maintaining gate drive under modulation: Important.

Depending on the particular circuit layout, the RF gate voltage may

fall as the drain voltage or current is increased, due to coupling

between the output circuitry including ground loop currents and the

gate circuit and/or driver. If the RF gate voltage falls too much under

modulation, the device will not be driven to saturation, causing

inefficiency, nonlinearity, destructive parasitic oscillations and

other serious problems. This is usually more apparent with analog

gate drive than with digital gate drive.

There are several high current paths in class E RF amplifiers. One

high current loop exists between the RF bypass capacitor at the DC end

of the primary of the output coupling transformer and the source bus.

Another exists between the shunt capacitor s and the source bus. Other

high current RF paths will occur within the output network.

You can generally avoid interaction between RF loops which exist in

the class E amplifier, and you gate circuit, by not using the ground

plane as a the other conductor for interconnecting the gate and

Analog Drive - Solder the ground side of gate driver transformer secondaries to the source bus immediately where the sources connect. Don t leave a lot of space between the secondary and the sources themselves.

Analog Drive Use twisted, balanced lines or shielded cable between the primaries of the gate driver transformers and the driver, and let the primaries float at the transformer end.

Keep the RF output circuitry far from any tuned driver circuits.

Digital Drive - When using driver ICs, terminate the cable s carrying input signal to the driver IC s with a resistor, and keep the leads short.

Digital Drive - Use a separate, short a few inches shielded cable for each driver IC, terminated at the IC, and brought back to a common feed point.

Digital Gate Drive using a Single or Multiple Driver ICs

One very practical way to provide gate drive to the final RF amplifier is

to use one of the several RF driver ICs available for the purpose. Some of

these driver ICs will operate on 30 mHz or higher. If you chose the correct

driver IC, it is possible to provide almost square wave drive to the gates of the RF amplifier MOSFETs,

which can result in more efficiency and will significantly reduce the possibly

of parasitic oscillations in the RF amplifier. Since the driver is not tuned,

it is possible to operate the driver on multiple bands, making multi band

operation much simpler. The driver ICs generally take a standard 5V TTL input

As of this writing, IXYS / DEI appear to provide the most robust driver ICs with

respect to RF service. The IXDD414 will drive a single FQA11N90 MOSFET quite well

at 7 mHz and below. These devices cost approximately 3.00 each. One driver IC

must be provided for each output MOSFET. The DEI DEIC420 will drive up to

5 FQA11N90 MOSFETs on 80 and 160 meters. The DEIC420 currently costs around

The DEIC420 is an rf packaged, high current, high frequency driver IC. It is

designed to work up to 45mHz into a few thousand PF or so, but will work

at lower frequencies into 15000pF or more. The input capacitance 5 FQA11N90 MOSFETs in parallel

will add up to about 15000pF. The DEIC420 will drive the 5 MOSFETs very well

up to 4mHz, making this a good driver for 80 and 160 meters.

a single driver IC is used per bank of MOSFETs, construction is relatively simple

and straight-forward. The IC requires 12 volts at over an Ampere. It is

recommended that you use a switching regulator such as the LM2576 rather than

a linear regulator. Provide a TTL signal to the IC s input at the operating frequency, and be

sure to properly terminate the coax cable carrying the input signal with a

100 ohm resistor to ground, and a 100 ohm resistor to a locally bypassed 5 volt source.

The IC must be well bypassed, as it is a high current, low impedance device. Use

more than one low impedance bypass capacitor of at least. 1uF to. 5uF per IC.

The main disadvantage of the DEIC420 is the cost - around

31.00 for a single part. Perhaps IXYS / DEI will consider a price reduction

for Amateurs using their products..

Using Multiple IXDD414 Driver ICs

The IXDD414 is a small, 5 pin TO220 packaged device capable of operating at

least up to the 40 meter band into a single FQA11N90 MOSFET. One practical

configuration involves driving 5 of the IXDD414 devices in parallel, and

connecting the output of each device to one gate of an FQA11N90 MOSFET, with

the MOSFET drains and sources connected in parallal. So, the inputs to the

drivers are in parallel, and the drains of the output MOSFETs are in parallel,

but the gates are not directly connected in parallel, but are driven identically

When using multiple driver ICs in a single class E stage, care must be taken

to ensre each driver IC receives the same input signal, and in exactly the same

phase. The most reliable method of accomplishing drive to the driver ICs is

to run a separate, short shielded cable to each driver IC, brought back to a

centeral point, and then fed using one piece of shielded cable.

Another method that can also work is to create a gate driver input bus from copper strap.

The physical construction should be as symmetrical as possible. Take care to

avoid any coupling between the driver IC input bus and the output, or parasitic

Driving the gates with an external transmitter

If you already own an RF source capable of supplying 30 or so watts of power,

you can use this transmitter to drive a 10 MOSFET transmitter on 75 and

160 meters. If the driver will put out 50 or 60 watts of power, you can use

Generally, since you are looking at a very low impedance when

driving the gates of MOSFETs, it is desirable to use a transformer to

step up the gate impedance to make it easier to drive with conventional

sources. A ratio of between 4:1 and 6:1 works very well for driving the

gates of MOSFETs. A single turn secondary is all that is necessary. Use

type 43 material for 160, 80 and 40 meters. The FB-43-1020 is a very

good core for the purpose. They cost approximately 2.50 each and are

available from CWS - BYTEMARK or Amidon. A single core is generally all

that is necessary for the driver transformer. There are many examples

and pictures of driver transformers presented in the RF amplifier

You will need to provide some kind of matching network between the driver

and the primaries of the gate transformers. An L network works very well

in this application. Most modern transmitters will not work well, or at all,

into a mismatched load. Proper matching between an external driver and the

Using a Dedicated Internal Driver

The procedure for using a dedicated driver is similar to using an external

transmitter for driving the gates. The driver itself will require a driver

of some type perhaps an external transmitter or driver IC. In essence,

the driver is really just another class E, D, or C amplifier used to driver

If the driver uses a resonant output such as with class E or class C drivers,

the driver will need to be tuned correctly for the operating frequency.

When using an intermediate driver that uses a resonant output, be sure the

output of the driver is stable over the entire band you wish to use. In general,

class E amplifiers deliver more output as the frequency is reduced. Make sure

you are not overdriving the gates in the low part of the band, and/or underdriving

the gates on the high end of the band.