Germanium transistors enjoyed their heyday during the first decade of semiconductor electronics before being widely replaced by microwave silicon devices. In this article, we will discuss why the first type of transistors is still considered an important element in the music industry and is of high importance for connoisseurs of good sound.
The birth of the element
Germanium was discovered by Clemens and Winkler in the German city of Freiberg in 1886. The existence of this element was predicted by Mendeleev, having set in advance its atomic weight equal to 71, and the density of 5.5 g/cm3.
In the early autumn of 1885, a miner working at the Himmelsfürst silver mine near Freiberg stumbled upon an unusual ore. It was given to Albin Weisbach from the nearby Mining Academy, who confirmed that it was a new mineral. He, in turn, asked his colleague Winkler to analyze the extraction. Winkler discovered thatof the found chemical element is 75% silver, 18% sulfur, the scientist could not determine the composition of the remaining 7% volume of the find.
By February 1886, he realized that this was a new metal-like element. When its properties were tested, it became clear that it was the missing element in the periodic table, which is located below silicon. The mineral from which it originated is known as argyrodite - Ag 8 GeS 6. In a few decades, this element will form the basis of germanium transistors for sound.
Germanium
At the end of the 19th century, germanium was first isolated and identified by the German chemist Clemens Winkler. This material, named after Winkler's homeland, has long been considered a low-conductivity metal. This statement was revised during the Second World War, since it was then that the semiconductor properties of germanium were discovered. Devices consisting of germanium became widespread in the postwar years. At this time, it was necessary to satisfy the need for the production of germanium transistors and similar devices. Thus, the production of germanium in the United States grew from a few hundred kilograms in 1946 to 45 tons by 1960.
Chronicle
The history of transistors begins in 1947 with Bell Laboratories, located in New Jersey. Three brilliant American physicists participated in the process: John Bardeen (1908-1991), W alter Brattain (1902-1987) and William Shockley (1910-1989).
The team led by Shockley tried to develop a new type of amplifier forUS telephone system, but what they actually invented turned out to be much more interesting.
Bardeen and Brattain built the first transistor on Tuesday, December 16, 1947. It is known as the point contact transistor. Shockley worked hard on the project, so it's no surprise that he was flustered and angry at being rejected. Soon he single-handedly formed the theory of the junction transistor. This device is superior in many respects to the point contact transistor.
The birth of a new world
While Bardeen left Bell Labs to become an academic (he went on to study germanium transistors and superconductors at the University of Illinois), Brattain worked for a while before moving on to teaching. Shockley started his own transistor manufacturing company and created a unique place - Silicon Valley. This is a thriving area in California around Palo Alto where major electronics corporations are located. Two of his employees, Robert Noyce and Gordon Moore, founded Intel, the world's largest chipmaker.
Bardeen, Brattain and Shockley briefly reunited in 1956 when they received the world's highest scientific award, the Nobel Prize in Physics, for their discovery.
Patent law
The original point-contact transistor design is outlined in a US patent filed by John Bardeen and W alter Brattain in June 1948 (about six months after the original discovery). Patent issued October 3, 1950of the year. A simple PN transistor had a thin top layer of P-type germanium (yellow) and a bottom layer of N-type germanium (orange). Germanium transistors had three pins: emitter (E, red), collector (C, blue), and base (G, green).
In simple terms
The principle of operation of a transistor sound amplifier will become clearer if we draw an analogy with the principle of operation of a water tap: the emitter is a pipeline, and the collector is a tap. This comparison helps explain how a transistor works.
Let's imagine that the transistor is a faucet. Electric current acts like water. The transistor has three terminals: base, collector and emitter. The base works like a faucet handle, the collector works like water running into the faucet, and the emitter works like a hole from which water flows out. By slightly turning the faucet handle, you can control the powerful flow of water. If you slightly turn the faucet handle, then the flow rate of water will increase significantly. If you completely close the faucet handle, the water will not flow. If you turn the knob all the way, the water will flow much faster.
Operation principle
As mentioned earlier, germanium transistors are circuits that are based on three contacts: emitter (E), collector (C) and base (B). The base controls the current from the collector to the emitter. The current that flows from the collector to the emitter is proportional to the base current. The emitter current, or base current, is equal to hFE. This setup uses a collector resistor (RI). If the current Ic flows throughRI, a voltage will be generated across this resistor, which is equal to the product of Ic x RI. This means that the voltage across the transistor is: E2 - (RI x Ic). Ic is approximately equal to Ie, so if IE=hFE x IB, then Ic is also equal to hFE x IB. Therefore, after the replacement, the voltage across the transistors (E) is E2 (RI x le x hFE).
Functions
The transistor audio amplifier is based on amplification and switching functions. Taking radio as an example, the signals that a radio receives from the atmosphere are extremely weak. The radio amplifies these signals through the speaker output. This is the "boost" function. So, for example, the germanium transistor gt806 is intended for use in pulse devices, converters and current and voltage stabilizers.
For an analog radio, simply amplifying the signal will make the speakers produce sound. However, for digital devices, the input waveform must be changed. For a digital device such as a computer or an MP3 player, the transistor must switch the signal state to 0 or 1. This is the "switching function"
You can find more complex components called transistors. We are talking about integrated circuits made from liquid silicon infiltration.
Soviet Silicon Valley
In Soviet times, in the early 60s, the city of Zelenograd became a springboard for the organization of the Microelectronics Center in it. Soviet engineer Shchigol F. A. develops the 2T312 transistor and its analogue 2T319, which later becamemain component of hybrid circuits. It was this man who laid the foundation for the production of germanium transistors in the USSR.
In 1964, the Angstrem plant, on the basis of the Research Institute of Precision Technologies, created the first IC-Path integrated circuit with 20 elements on a chip, which performs the task of a combination of transistors with resistive connections. At the same time, another technology appeared: the first flat transistors "Plane" were launched.
In 1966, the first experimental station for the production of flat integrated circuits began to operate at the Pulsar Research Institute. At NIIME, Dr. Valiev's group started manufacturing linear resistors with logic integrated circuits.
In 1968, the Pulsar Research Institute produced the first part of KD910, KD911, KT318 thin-film open-frame flat transistor hybrid ICs, which are designed for communication, television, radio broadcasting.
Linear transistors with mass-use digital ICs (type 155) were developed at the DOE Research Institute. In 1969, the Soviet physicist Zh. I. Alferov discovered to the world the theory of controlling electron and light fluxes in heterostructures based on the gallium arsenide system.
Past versus future
The first serial transistors were based on germanium. P-type and N-type germanium were connected together to form a junction transistor.
The American company Fairchild Semiconductor invented the planar process in the 1960s. Here for the production of transistors withsilicon and photolithography have been used for improved industrial scale reproducibility. This led to the idea of integrated circuits.
Significant differences between germanium and silicon transistors are as follows:
- silicon transistors are much cheaper;
- silicon transistor has a threshold voltage of 0.7V while germanium has a threshold voltage of 0.3V;
- silicon withstands temperatures around 200°C, germanium 85°C;
- silicon leakage current is measured in nA, for germanium in mA;
- PIV Si is larger than Ge;
- Ge can detect small changes in signals hence they are the most "musical" transistors due to their high sensitivity.
Audio
To get high-quality sound on analog audio equipment, you need to decide. What to choose: modern integrated circuits (ICs) or ULF on germanium transistors?
In the early days of transistors, scientists and engineers argued over the material that would underlie the devices. Among the elements of the periodic table, some are conductors, others are insulators. But some elements have an interesting property that allows them to be called semiconductors. Silicon is a semiconductor and is used in almost all transistors and integrated circuits manufactured today.
But before silicon was used as a suitable material for making a transistor, it was replaced by germanium. The advantage of silicon over germanium was mainly due to the higher gain that could be achieved.
Although germanium transistors from different manufacturers often have different characteristics from each other, some types are considered to produce a warm, rich and dynamic sound. Sounds can range from crunchy and uneven to muffled and flat with in-between. Undoubtedly, such a transistor deserves further study as an amplifying device.
Advice for action
Buying up radio components is a process in which you can find everything you need for your work. What do the experts say?
According to many radio amateurs and connoisseurs of high-quality sound, the P605, KT602, KT908 series are recognized as the most musical transistors.
For stabilizers, it is better to use the AD148, AD162 series from Siemens, Philips, Telefunken.
Judging by the reviews, the most powerful of the germanium transistors - GT806, it wins compared to the P605 series, but in terms of timbre frequency, it is better to give preference to the latter. It is worth paying attention to the type KT851 and KT850, as well as the field-effect transistor KP904.
It is not advised to use P210 and ASY21 types as they actually have poor sound characteristics.
Guitars
Although different brands of germanium transistors have different characteristics, they can all be used to create a dynamic, richer and more enjoyable sound. They can help change the sound of a guitarin a wide range of tones, including intense, muted, harsh, smoother, or a combination of these. In some devices, they are widely used to give guitar music a great playing, extremely tangible and soft sound.
What is the major disadvantage of germanium transistors? Of course, their unpredictable behavior. According to experts, it will be necessary to carry out a grandiose purchase of radio components, that is, to purchase hundreds of transistors in order to find the right one for you after repeated testing. This shortcoming was identified by studio engineer and musician Zachary Vex while searching for vintage sound effects blocks.
Vex began creating Fuzz guitar effects units to make guitar music sound clearer by mixing the original Fuzz units in certain proportions. He used these transistors without testing their potential to get the best combination, relying solely on luck. In the end, he was forced to abandon some transistors due to their unsuitable sound and began to produce good Fuzz blocks with germanium transistors in his factory.
