MICROWAVES CHAPTER 9

SOLID STATE DEVICE

An electronic device in which electricity flows through solid semiconductor crystals (silicon, gallium arsenide, germanium) rather than through vacuum tubes.

VACUUM TUBE

An electron tube containing a near-vacuum that allows the free passage of electric current.

MICROWAVE DIODES

In the RF spectrum, these can amplify, oscillate, mix, detect, attenuate, and switch a high frequency signal in the appropriate circuit.

POINT CONTACT DIODE

Oldest microwave semiconductor device.

Ideal for low-signal applications and are widely used in microwave mixers and detectors.

They are extremely delicate and cannot withstand high power.

They are easily damaged, and, therefore must be used in such a way as to avoid shock and vibration.

PIN

TYPES OF MICROWAVE DIODES
which attenuate or switch

Schottky

TYPES OF MICROWAVE DIODES
which mix or detect

Tunnel

TYPES OF MICROWAVE DIODES
(which amplify or oscillate)

Gunn

TYPES OF MICROWAVE DIODES
which also oscillate

Varactor diodes

TYPES OF MICROWAVE DIODES
multipliers

SCHOTTKY DIODES

• Consists of a semiconductor (usually N-type) and a metal that comes in contact with the semiconductor.

• It is a general-purpose diode that usually is used for mixer and detector applications at those higher frequencies.

unipolar action

• this makes the Schottky diode ideal for RF and microwave applications, because the diode can respond to high frequencies without distorting the output or causing other problems.

The series inductance

EQUIVALENT CIRCUIT OF A SCHOTTKY DIODE
- is the inductance of the bonding wires that go from the actual diode chip to the connections to the outside world.

The series resistance

total resistance in the diode, including that of the semiconductor and the substrate on which the diode is mounted.
EQUIVALENT CIRCUIT OF A SCHOTTKY DIODE

The junction capacitance

the capacitance that is present across the actual junction between the semiconductor and the metal.
EQUIVALENT CIRCUIT OF A SCHOTTKY DIODE

The overlay capacitance

across the combination of the semiconductor and the substrate.
EQUIVALENT CIRCUIT OF A SCHOTTKY DIODE

speed, majority carrier

ADVANTAGES OF SCHOTTKY DIODES
The use of a Schottky diode generally allows ICs to have greater — because it is a — device. Having a low carrier lifetime attributes to its greater switching speeds.

integrated circuit (IC)

ADVANTAGES OF SCHOTTKY DIODES
When incorporated into —- technologies the Schottky diode enhances the range of diodes available.

turn-on voltages

The Schottky diodes have lower —- because of the lower barrier height of the rectifying metal-to-semiconductor junction.
ADVANTAGES OF SCHOTTKY DIODES

PIN DIODES