Germanium transistors experienced their heyday during the first decade of semiconductor electronics, before they were widely replaced by ultra-high frequency 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 great importance for connoisseurs of good sound.
Element Origin
Germanium was discovered by Clemens and Winkler in the German city of Freiberg in 1886. The existence of this element was predicted by Mendeleev, setting in advance its atomic weight equal to 71, and a density of 5.5 g / cm 3 .
In the early fall of 1885, a miner who worked at the Himmelsfürst silver mine near Freiberg stumbled upon an unusual ore. It was handed over 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 prey. Winkler found that the chemical element contained 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 this is the missing element in the periodic table, which is located below silicon. The mineral from which it came from is known as argyrodite - Ag 8 GeS 6. After several decades, this element will act as 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 conductive 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 were 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 Germany in the United States grew from several hundred kilograms in 1946 to 45 tons by 1960.
Chronicle
The history of transistors begins in 1947 with the company Bell Laboratories, located in New Jersey. Three brilliant American physicists took part in the process: John Bardin (1908–1991), Walter Brattain (1902–1987) and William Shockley (1910–1989).
The team, led by Shockley, tried to develop a new type of amplifier for the US telephone system, but what they actually invented turned out to be much more interesting.
Bardin and Brattain built the first transistor on Tuesday, December 16, 1947. It is known as a point contact transistor. Shockley worked a lot on the project, so it is not surprising that he was excited and angry that he was rejected. Soon, he single-handedly formed the theory of a transient transistor. This device is superior in many respects to a point contact transistor.
The birth of a new world
While Bardin quit Bell Labs to become an academician (he continued to study germanium transistors and superconductors at the University of Illinois), Brattain worked for some more time, and then went to pedagogy. Shockley founded his own transistor company and created a unique place - Silicon Valley. This is a thriving area in California around Palo Alto, where large electronics corporations are located. Two of its employees, Robert Noyce and Gordon Moore, founded Intel, the world's largest chip maker.
Bardin, Brattain and Shockley reunited briefly in 1956: for their discovery they received the world's highest scientific award - the Nobel Prize in Physics.
Patent law
The original design of the point-contact transistor is described in a US patent by John Bardin and Walter Brattain, registered in June 1948 (approximately six months after the initial discovery). The patent was granted on October 3, 1950. A simple PN transistor had a thin upper layer of P-type germanium (yellow) and a lower layer of N-type germanium (orange). Germanium transistors had three contacts: emitter (E, red), collector (C, blue) and base (G, green).
In simple words
The principle of operation of the sound amplifier on transistors will become clearer if we draw an analogy with the principle of the water tap: the emitter is a pipeline, and the collector is a tap. This comparison helps explain how the transistor works.
Imagine that a transistor is a water tap. Electric current acts like water. The transistor has three contacts: base, collector and emitter. The base acts as a faucet handle, the collector as water flowing into a faucet, and the emitter as a hole from which water flows. Slightly turning the handle of the tap can hold back a powerful flow of water. If you turn the tap knob slightly, then the flow rate of water will increase significantly. If the handle of the tap is completely closed, water will not flow. If you turn the handle completely, then the water will pour much faster.
Operating principle
As mentioned earlier, germanium transistors are circuits that have three contacts at the base: 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 hFE. This setting uses a collector resistor (RI). If the current Ic flows through RI, a voltage will be generated on this resistor, which is equal to the product Ic x RI. This means that the voltage across the transistor is equal to: E2 - (RI x Ic). Ic is approximately equal to Ie, therefore, 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 sound amplifier on transistors is built on the amplification and switching functions. If we take radio as an example, the signals that the radio receives from the atmosphere are extremely weak. The radio amplifies these signals through the speaker output. This is the gain function. So, for example, the gt806 germanium transistor is intended for use in pulse devices, converters and current and voltage stabilizers.
For analogue radio, simply amplifying the signal will cause the speakers to 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 a “switch function”
More complex components called transistors can be found. It's about integrated circuits made of 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 Center for Microelectronics in it. The Soviet engineer Schigol F.A. is developing a 2T312 transistor and its analog 2T319, which subsequently became the main component of hybrid circuits. It was this man who laid the foundation for the release of germanium transistors in the USSR.
In 1964, the Angstrem plant, on the basis of the Scientific Research Institute of Precise Technologies, created the first IC-Path integrated circuit with 20 elements on a chip that performs the task of a set of transistors with resistive connections. At the same time, another technology appeared: the first Flat Transistors 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 team began manufacturing line resistors with logic integrated circuits.
In 1968, the Pulsar Research Institute produced the first part of thin-film hybrid ICs with flat transistors with open frame types KD910, KD911, KT318, which are designed for communication, television, broadcasting.
Linear transistors with digital ICs for mass use (type 155) were developed at the Research Institute of ME. In 1969, the Soviet physicist Alferov, J. I., discovered the theory of electron and light flux control in heterostructures based on a gallium arsenide system.
Past vs Future
The first serial transistors were based on germanium. The P-type and N-type germanium were connected together to form a transition transistor.
Fairchild Semiconductor, an American company, invented the planar process in the 1960s. Here, silicon and photolithography were used to manufacture transistors with improved reproducible characteristics on an industrial scale. This led to the idea of integrated circuits.
Significant differences between germanium and silicon transistors are as follows:
- silicon transistors are much cheaper;
- the silicon transistor has a threshold voltage of 0.7 V, while germanium is 0.3 V;
- silicon withstands temperatures of about 200 ° C, germanium - 85 ° C;
- silicon leakage current is measured in nA, for Germany - in mA;
- PIV Si is larger than Ge;
- Ge can detect small changes in signals, therefore, 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 with germanium transistors?
In the early days of the advent of transistors, scientists and engineers argued about the material that would underlie the operation of 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 began to be used as a suitable material for the manufacture of the 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, it is believed that some types give a warm, rich and dynamic sound. Sounds can vary from crispy and uneven to muffled and even with intermediate between them. Undoubtedly, such a transistor deserves further study as an amplifier device.
Tips 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 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 of the brands Siemens, Philips, Telefunken.
Judging by the reviews, the most powerful of the Germanium transistors - GT806, it wins in comparison with the P605 series, but it is better to give preference to the latter in terms of tone frequency. It is worth paying attention to the type KT851 and KT850, as well as the KP904 field effect transistor.
They are not advised to use types P210 and ASY21, since in fact they have poor sound characteristics.
Guitars
Although germanium transistors of different brands differ in characteristics, they can all be used to create a dynamic, more saturated and pleasant sound. They can help change the sound of the guitar in a wide range of tones, including intense, muffled, sharp, more even or a combination of them. In some devices, they are widely used to give the guitar music an excellent gaming, extremely tangible and soft sound.
What is the significant 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 acquire hundreds of transistors in order to find the right one after repeated testing. This flaw was identified by studio engineer and musician Zachary Veks while searching for vintage blocks for sound effects.
Wex began to create effect blocks for Fuzz guitars to make the sound of guitar music clear by combining the original Fuzz blocks in a certain ratio. He used these transistors without testing their potential to get the best combination, relying solely on luck. As a result, he was forced to abandon some transistors due to their inappropriate sound and began to produce good Fuzz blocks with germanium transistors in his factory.