Charge Q [coulomb]

Voltage V = dU/dQ [volts]

Current I= dQ/dt [ampere]

Capacitance C = dQ/dV [farad]

Inductors V = -LdI/dt [henry]

Resistance R = V / I [ohm]

Power P = V*I [watt]

Energy U = P dt [joule]

e = 1.602 x 10-19

Ltot = Σ(Li) 1/Ltot = Σ(1/Li)

1/Ctot = Σ(1/Ci) Ctot = Σ(Ci)

IB + IC + ID - IA = 0

IB + IC + ID = IA

Semiconductors:

P and N type semiconductor material

One of the crucial keys to solid state electronics is the nature of the P-N junction. When p-type and n-type materials are placed in contact with each other, the junction behaves very differently than either type of material alone. Specifically, current will flow readily in one direction (forward biased) but not in the other (reverse biased), creating the basic diode. This non-reversing behavior arises from the nature of the charge transport process in the two types of materials.

In the p-type region there are holes from the acceptor impurities and in the n-type region there are extra electrons.

When a p-n junction is formed, some of the electrons from the n-region which have reached the conduction band are free to diffuse across the junction and combine with holes.

Filling a hole makes a negative ion and leaves behind a positive ion on the n-side. A space charge builds up, creating a depletion region which inhibits any further electron transfer unless it is helped by putting forward bias on the junction

The nature of the p-n junction is that it will conduct current in the forward direction but not in the reverse direction.

Molecular Beam Epitaxy (MBE)

Silicon nitrate

Potassium Hydroxide

photoresist

Carbon trifluoride

Etchant and ratio of mixture Material Etched Approx. etch rate µ m/min @ 20°C

HCl (conc.) InP 5-15

HCl (conc.) Surface oxide on GaAs Fast

HCl (conc.) InGaAs <0.02

HCl:H20 (2:1) InP 8

HCl:H2O (1:1) InP 0.7

HCl:H2O (1:2) InP 0.09

H3PO4:HCl (1:1) InP 2.5

H3PO4:HCl (1:2) InP 4.8

H3PO4:HCl (1:3) InP 6.6

H3PO4:HCl (3:1) InP 0.75

H3PO4:H2O2:H2O (3:4:3) GaAs 6

H2O:NH4OH:H2O2 (20:2:1) GaAs 0.5

HBr:CH3COOH:K2Cr2O7 (1:1:1) Most III-V compounds 2-5

H2O2:NH4OH:H2O (0.7:2:100) GaAs 0.1

H2SO4:H2O2:H20 (1:8:80) InGaAs 0.5

Br:CH3OH (1:100) Most III-Vs 1-10

HCl:H2O2:H2O (1:4:80) GaAs 1

pnp

npn

When used as a switch, the bipolar junction transistor (BJT) must be biased onto a different part of the output characteristic curves. For an amplifier, the linear part of the output curve is employed, as a switch, the BJT is operated on regions of the output curves known as saturation and cut-off. The yellow shaded area represents the "cut-off" region. Here the operating conditions of the transistor are zero input base current, zero output collector current and maximum (supply rail) collector voltage. In "saturation", as depicted by the red shaded area, the BJT will be biased so that the maximum amount of base current is applied, resulting in maximum collector current flow and minimum collector emitter voltage. In both cut-off and saturation, minimum power is dissipated in the transistor

npn

Bipolar transistor: Switch OR Amplifier

This configuration is used for high frequency applications because the base separates the input and output, minimizing oscillations at high frequency. It has a high voltage gain, relatively low input impedance and high output impedance compared to the common collector.

NPN common base amplifier

The common emitter configuration lends itself to voltage amplification and is the most common configuration for transistor amplifiers.

npn

Rload

Rs

signal

From Analog to Digital : TTL, xMOS

TTL

The transistor-transistor-logic (TTL) family was developed in the use of transistor switches for logical operations and defines the binary values as

0 V to 0.8 V = logic 0 2 V to 5 V = logic 1

TTL are inexpensive, but draw a lot of power and must be supplied with +5 volts. Individual gates may draw 3 to 4 mA. The low power Schottky versions draw only 20% of the power, but are more expensive.

CMOS

The complementary metal oxide semiconductor family (CMOS) has equivalents to most of the TTL chips. CMOS chips are much lower in power requirements (drawing about 1 mA) and operate with a wide range of supply voltages (typically 3 to 18 volts). A drawback is extreme sensitivity to static electricity - they must be

carefully protected from static discharges.

NMOS and PMOS

P- and N-channel Metal Oxide Semiconductors (PMOS and NMOS) offer the advantage of higher component

density than TTL chips. They are sensitive to damage from electrical discharge.

NAND Gate IC7400