True History of the Transistor

http://www.bn.com.br/radios-antigos/semicond.htm
The transistor was invented in the Beel Telephone Laboratories in December 1947 (not 1948 as is often said) by Bardeen and Brattain.
Discovered so to speak (since they were looking for a solid state device equivalent to the vacuum tube), accidentally during studies of surfaces around a point-contact diode.
The transistors were therefore of type point-contact "and there is evidence that Shockley, the theorist who headed the research was pissed because the device was not what I was looking for. At the time, he was looking for a semiconductor amplifier similar to what we now call "junction FET.
The name transistor was derived from their intrinsic properties "transfer resistor" in English: (transfer resistor). Bell Labs kept the discovery secret until June 1948 (hence the confusion with the dates of discovery).
With a estrodosa publicity, they announced their findings publicly, but few people realized the significance and importance of the publication, despite having left the front pages of newspapers.
Although it was a great scientific achievement, the transistor not reached immediately, the commercial supremacy. The difficulties of manufacturing added to the high price of germanium, a rare element, kept the price too high. The best transistors costing $ 8 a time when the price of a valve was only 75 cents.
Shochley ignored the point-contact transistor and continued his research in other directions. He reoriented his ideas and developed the theory of "transistor junction".
In July 1951, Bell announced the creation of this device. In September 1951 they promote a symposium and are willing to license the new technology of both types of transistors to any company that was willing to pay $ 25,000.00.
This was the beginning of the industrialization of the transistor.
Many firms withdrew the notice of license. Former manufacturers of vacuum tubes, such as RCA, Raytheon, GE and industrial leaders in the market like Texas and Transitron.
Many started the production of point-contact transistor, which at that time, worked better in high frequency than the types of joint. However, the junction transistor becomes faster, far superior in performance and is simpler and easier to manufacture.
The point-contact transistor was made obsolete by about 1953 in America and later in England.
Only a few thousand were manufactured between 120 types, many Americans (not including these numbers, trial versions).

The first junction transistor manufactured commercially was primitive compared to modern devices, with a maximum voltage between collector-emitter of 6 volts and a maximum current of a few milliamps.
Particularly notable was the Raytheon CK722 transistor 1953, the first device solid state electronic mass produced available to the amateur builder. Various types of transistors have been developed, increasing the frequency response by reducing noise levels and increasing its power capacity.
In England, two companies have maintained research labs not so early as in America: Standard Telephones and Cables (STC) and General Electric Company of England "GEC" (no telação with the American GE).
Research was conducted in France and Germany without trade effects.
In 1950, a shark comes in this small pond: the Dutch PHILIPS by Mullard, its English subsidiary, with a complete plan to industrialize the transistor.
The goal was to dominate the Philips 95% of the European market, reaching this goal in few years. The series 'OC' transistor dominated Europe for over 20 years.
The former were made of germanium transistors, a semiconductor metal, but soon found that the silicon offered a number of advantages over germanium. The silicon was more difficult to refine because of its high melting point, but in 1955 the first silicon transistor was already sold.
Texas Instruments was one of the companies that took part in the initial development of this technology by launching a series of devices known at the time by the letters "900" and "2s".
The big turnaround came in 1954 when Gordon Teal perfected a junction transistor made of silicon.
The silicon instead of germanium, a mineral is abundant, only losing in the oxygen availability. This fact, coupled with the improvement of production techniques, have significantly decreased the price of the transistor. This enabled him to popularize and would cause a revolution in the computer industry. That only such a revolution would be repeated with the creation and refinement of integrated circuits.
Major innovations in the field of semiconductors

INNOVATION / LABORATORY / YEAR
POINT OF CONTACT TRANSISTOR / Bell Labs-Western Electric / 1947
CULTIVATION IN SINGLE CRYSTAL / Western Electric / 1950
ZONE REFINED / Western Electric / 1950
TRANSISTOR JUNCTION CULTURED / Western Electric / 1951
SILICON TRANSISTOR / Texas Instruments / 1954
MASK OF OXIDE AND DIFFUSION / Western Electric / 1955
PLANAR TRANSISTOR / Fairchild / 1960
INTEGRATED CIRCUIT / Texas Instruments, Fairchild / 1961
GUNN DIODE / IBM / 1963

Resistance

/ The electrical resistance of a circuit component or device is defined as the ratio of the voltage applied to the electric current whichflows through it:

If the resistance is constant over a considerable range of voltage, then Ohm's law, I = V/R, can be used to predict the behavior of the material. Although the definition above involves DC current and voltage, the same definition holds for the AC application of resistors.

Whether or not a material obeys Ohm's law, its resistance can be described in terms of its bulk resistivity. The resistivity, and thus the resistance, is temperature dependent. Over sizable ranges of temperature, this temperature dependence can be predicted from a temperature coefficient of resistance.

Resistivity and Conductivity

The electrical resistance of a wire would be expected to be greater for a longer wire, less for a wire of larger cross sectional area, and would be expected to depend upon the material out of which the wire is made. Experimentally, the dependence upon these properties is a straightforward one for a wide range of conditions, and the resistance of a wire can be expressed as

The factor in the resistance which takes into account the nature of the material is the resistivity . Although it is temperature dependent, it can be used at a given temperature to calculate the resistance of a wire of given geometry.

The inverse of resistivity is called conductivity. There are contexts where the use of conductivity is more convenient.

Electrical conductivity = σ = 1/ρ

Resistor Combinations

The combination rules for any number of resistors in series or parallel can be derived with the use of Ohm's Law, the voltage law, and the current law.

Resistivity Calculation

The electrical resistance of a wire would be expected to be greater for a longer wire, less for a wire of larger cross sectional area, and would be expected to depend upon the material out of which the wire is made (resistivity). Experimentally, the dependence upon these properties is a straightforward one for a wide range of conditions, and the resistance of a wire can be expressed as

Resistance = resistivity x length/area

Parte superior do formulário

For a wire of length L = m = ft
and area A = cm2
corresponding to radius r = cm
and diameter inches for common wire gauge comparison
with resistivity = ρ = x 10^ ohm meters
will have resistance R = ohms.

Parte inferior do formulário

Enter data and then click on the quantity you wish to calculate in the active formula above. Unspecified parameters will default to values typical of 10 meters of #12 copper wire. Upon changes, the values will not be forced to be consistent until you click on the quantity you wish to calculate.

Commonly used U.S. wire gauges
for copper wire.
AWG / Diameter
(inches) / Typical use
10 / 0.1019 / Electric range
12 / 0.0808 / Household circuit
14 / 0.0640 / Switch leads
/ Resistivities of some metals
in ohm-m(x 10-8) at 20°C.
Aluminum / 2.65 / Gold / 2.24
Copper / 1.724 / Silver / 1.59
Iron / 9.71 / Platinum / 10.6
Nichrome / 100 / Tungsten / 5.65

Resistor-Transistor Logic

Consider the most basic transistor circuit, such as the one shown to the left. We will only be applying one of two voltages to the input I: 0 volts (logic 0) or +V volts (logic 1). The exact voltage used as +V depends on the circuit design parameters; in RTL integrated circuits, the usual voltage is +3.6v. We'll assume an ordinary NPN transistor here, with a reasonable dc current gain, an emitter-base forward voltage of 0.65 volt, and a collector-emitter saturation voltage no higher than 0.3 volt. In standard RTL ICs, the base resistor is 470 and the collector resistor is 640.

When the input voltage is zero volts (actually, anything under 0.5 volt), there is no forward bias to the emitter-base junction, and the transistor does not conduct. Therefore no current flows through the collector resistor, and the output voltage is +V volts. Hence, a logic 0 input results in a logic 1 output.

When the input voltage is +V volts, the transistor's emitter-base junction will clearly be forward biased. For those who like the mathematics, we'll assume a similar output circuit connected to this input. Thus, we'll have a voltage of 3.6 - 0.65 = 2.95 volts applied across a series combination of a 640 output resistor and a 470 input resistor. This gives us a base current of:

2.95v / 1110 = 0.0026576577 amperes = 2.66 ma.

RTL is a relatively old technology, and the transistors used in RTL ICs have a dc forward current gain of around 30. If we assume a current gain of 30, 2.66 ma base current will support a maximum of 79.8 ma collector current. However, if we drop all but 0.3 volts across the 640 collector resistor, it will carry 3.3/640 = 5.1 ma. Therefore this transistor is indeed fully saturated; it is turned on as hard as it can be.

With a logic 1 input, then, this circuit produces a logic 0 output. We have already seen that a logic 0 input will produce a logic 1 output. Hence, this is a basic inverter circuit.

As we can see from the above calculations, the amount of current provided to the base of the transistor is far more than is necessary to drive the transistor into saturation. Therefore, we have the possibility of using one output to drive multiple inputs of other gates, and of having gates with multiple input resistors. Such a circuit is shown to the right.

In this circuit, we have four input resistors. Raising any one input to +3.6 volts will be sufficient to turn the transistor on, and applying additional logic 1 (+3.6 volt) inputs will not really have any appreciable effect on the output voltage. Remember that the forward bias voltage on the transistor's base will not exceed 0.65 volt, so the current through a grounded input resistor will not exceed 0.65v/470 = 1.383 ma. This does provide us with a practical limit on the number of allowable input resistors to a single transistor, but doesn't cause any serious problems within that limit.

The RTL gate shown above will work, but has a problem due to possible signal interactions through the multiple input resistors. A better way to implement the NOR function is shown to the left.

Here, each transistor has only one input resistor, so there is no interaction between inputs. The NOR function is performed at the common collector connection of all transistors, which share a single collector load resistor.

This is in fact the pattern for all standard RTL ICs. The very commonly-used µL914 is a dual two-input NOR gate, where each gate is a two-transistor version of the circuit to the left. It is rated to draw 12 ma of current from the 3.6V power supply when both outputs are at logic 0. This corresponds quite well with the calculations we have already made.

Standard fan-out for RTL gates is rated at 16. However, the fan-in for a standard RTL gate input is 3. Thus, a gate can produce 16 units of drive current from the output, but requires 3 units to drive an input. There are low-power versions of these gates that increase the values of the base and collector resistors to 1.5K and 3.6K, respectively. Such gates demand less current, and typically have a fan-in of 1 and a fan-out of 2 or 3. They also have reduced frequency response, so they cannot operate as rapidly as the standard gates. To get greater output drive capabilities, buffers are used. These are typically inverters which have been designed with a fan-out of 80. They also have a fan-in requirement of 6, since they use pairs of input transistors to get increased drive.

We can get a NAND function in either of two ways. We can simply invert the inputs to the NOR/OR gate, thus turning it into an AND/NAND gate, or we can use the circuit shown to the right.

In this circuit, each transistor has its own separate input resistor, so each is controlled by a different input signal. However, the only way the output can be pulled down to logic 0 is if both transistors are turned on by logic 1 inputs. If either input is a logic 0 that transistor cannot conduct, so there is no current through either one. The output is then a logic 1. This is the behavior of a NAND gate. Of course, an inverter can also be included to provide an AND output at the same time.