Single stage AF amplifier. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Beginner radio amateur
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This is the simplest design that allows you to demonstrate the amplifying capabilities of a transistor. True, the voltage gain is small - it does not exceed 6, so the scope of such a device is limited. Nevertheless, it can be connected to, say, a detector radio receiver (it must be loaded with a 10 kΩ resistor) and, using the BF1 headphone, listen to the transmission of a local radio station.
The amplified signal is fed to the input sockets X1, X2, and the supply voltage (as in all other designs of this author, it is 6 V - four galvanic cells with a voltage of 1,5 V connected in series) is fed to the sockets X3, X4. The divider R1 R2 sets the bias voltage at the base of the transistor, and the resistor R3 provides current feedback, which contributes to the temperature stabilization of the amplifier.
How does stabilization take place? Suppose that under the influence of temperature, the collector current of the transistor has increased. Accordingly, the voltage drop across the resistor R3 will increase. As a result, the emitter current will decrease, and hence the collector current - it will reach its original value.
The load of the amplifying stage is a headphone with a resistance of 60 ... 100 Ohms.
It is not difficult to check the operation of the amplifier, you need to touch the X1 input jack, for example, with tweezers - a weak buzz should be heard in the phone as a result of AC interference. The collector current of the transistor is about 3 mA.
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Physicists from the University of Berkeley in the US have created the world's first transistor with a gate of about one nanometer. This is an order of magnitude less than the smallest transistors in use today. An article by scientists was published in the journal Science, the university website briefly talks about the development.
The materials for the transistor were molybdenum sulfide and carbon nanotubes, it was this combination that made it possible to radically reduce the size of the gate - it is this element of the device that controls its conductivity. The design involves three layers: a silicon substrate, zirconium dioxide plates with a carbon nanotube passing through them, and a thin film of molybdenum disulfide.
Due to the higher resistance of molybdenum disulfide than silicon, the gate of even a single carbon nanotube creates a strong electric field to prevent electrons from "jumping" from one end of the transistor to the other using quantum tunneling.
"We have created the smallest transistors to date. The nanometer gate device proves that the right choice of materials allows further reduction in the size of electronics," said research team member Ali Javey.
It is impossible to use such transistors for electronics right now, since there is no technology for printing them and embedding them in chips, but this is a task for the future.
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