Electronics Engineering (Semiconductors IV)
Other Types of Diodes
Point Contact Diode- Having a fine wire whose point is in permanent contact with the surface of a water of semiconductor material.
Schottky diode- Other names are surface barrier or hotcarrier or hot-electron diode. Rectifying metal-semiconductor junction. Better than point-contact diode in terms of noise figure. Current flow is not accompanied by hole movement only electrons.
Tunnel Diode- Forward conduction characteristic displays ”negative resistance”. Utilizes a heavily doped material, and therefore have so many free electrons. Also called esaki diode.
Gunn Diode- With negative resistance that depends on a specific form of quantum-mechanical band structure. Exhibits Gunn effect. Gunn effect – the appearance of RF current oscillations in a DC biased slab of n-type gallium arsenide in a 3kV electric field. With wide range of tunability. Also called transferred electron oscillator.
Read Diode- With negative resistance that is due to the phase shift between the applied voltage and its current. It consists of two regions, a narrow avalanche region and relatively long drift region. Basis of IMPATT and TRAPATT diode.
IMPATT Diode- Impact Avalanche Transit-Time. A practical Read Diode with a P-type drift region. Used in microwave.
TRAPATT Diode- Trapped-Plasma-Avalanche Triggered Transit. Similar with IMPATT except for an N-type drift region instead of P-type.
TUNNETT- Tunnel Transit-Time. Operation is based on the combination of tunneling (Tunnel diode) and transit-time of IMPATT. Used in microwave.
MITATT- Mixed Tunneling and Avalanche Transit Time. Also used in microwave.
BARITT- Barrier-Injection Transit-Time. Also used in microwave.
Backward Diode- Operated in reverse direction. Designed such that its high current low takes place when the junction is reverse biased.
PIN Diode- P-type – intrinsic – n-type diode. The intrinsic material offers an impedance at microwave frequencies controllable by a lower frequency or DC bias.
Light Emitting Diode- Semiconductor diode that emits visible light when forward biased. Commonly uses Gallium Arsenide Phosphide (GaAsP) or simply Gallium PhosphViderey.
Photo Diode- Semiconductor diode whose current increases as light strikes into its opening. Usually operated in reverse-biased and dependent on the leakage of reverse saturation current.
Thyrector- Viewed as two zener diode connected backto-back series (both cathodes are joined). A bi-directional trigger device.
DIAC or Diode AC- A three layer semiconductor device that exhibits very high resistance up to certain voltage VBR , beyond which the device exhibits negative resistance. Viewed as a gateless TRIAC. Bidirectional Trigger device.
Shockley Diode- A four layer diode. A dual terminal pnpn device. A unilateral or unidirectional break-over device.
Diode Circuits
Half-wave rectifier
Conducts for only 180 deg of input. Ripple frequency = input frequency
VDC = Vp / Π =0.318Vp
Ripple Factor:
r = Vrms / VDC
= 0.385Vp/0.318Vp
= 1.21
PIV = 1.414Vrms
Full-wave rectifier
Conducts for 3600 of input. Applies two different frequencies for both types.
VDC = 2Vp /Π = 0.636Vp
Vrms = Vp /2˄(1/2)
PIV = 1.414Vrms
Ripple Frequency = 2[AC input frequency]
Types of Full-wave Rectifier
Bridge Type
Center Tapped
Clamper Circuit
A circuit which adds a fixed bias to a wave at each occurrence at some predetermined feature of the wave. Also called DC restorer.
Multiplier Circuit
Increases the peak value of the input voltage. Uses clamping action. Can be doubler, tripler or quadrupler.