LF generator on a tunnel diode. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Radio amateur designer
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The simplest of all tunnel diode devices are generators. Unlike transistor oscillators, they do not need a special feedback circuit, so both the circuit and the design are very simple. The scheme of the proposed generator is shown in the figure. Resistor R1, diode VD1 and capacitor C1 form the operating point voltage of the tunnel diode. It is equal to the direct voltage drop across the open junction of the VD1 diode and is largely stabilized with changes in battery voltage. The operating point is located on the falling section of the current-voltage characteristic of the tunnel diode VD2.
A low-frequency oscillatory circuit L2C1 is connected to the tunnel diode VD2, in which oscillations are excited. Directly from this circuit, the low-frequency voltage is supplied to high-resistance telephones BF1.
For normal excitation of the generator, it is necessary that the peak current of the tunnel diode is within 1 ... 2 mA, the peak voltage is 60 ... 100 mV. Therefore, the generator can be assembled on a tunnel diode of any type with the specified parameters. In addition, it is necessary that the active resistance of the coil L1 does not exceed 5 ohms, and its inductance is several tens of millihenries. The author used a W-shaped magnetic circuit made of transformer steel with a cross section of 0,5 cm2 on the frame of which, coil to coil, wound 400 turns of PEL wire with a diameter of 0,25 mm. As a coil L1, you can also try to use half of the primary winding or the secondary winding of the output transformer from the transistor receiver. To obtain the desired tone of sound vibrations, the capacitance of the capacitor C2 must be selected within 0,01 ... 1 μF.
As a power source for the generator, you can use a silicon photocell that develops a current of 3 ... 4 mA. To do this, it is connected instead of the stabilizing diode VD1. Resistor R1 and an external power supply are not needed in this case. The generator starts working when the photocell is brightly illuminated.
The scope of the proposed generator is quite wide. It can serve as a signal source when setting up low-frequency equipment, when studying telegraph Morse code, and when powered by a photocell, as an indicator of the illumination of a room or workplace. When developing the generator, materials from the book were used: Goryunov N.N. etc. Schemes on tunnel diodes. - M.-L.: "Energy", MRB, 1965.
Author: S. Kovalenko, Kstovo, Nizhny Novgorod Region
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