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Experiments with a tunnel diode analog

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Experiments with a tunnel diode analog
In addition to tunnel diode , it is interesting to conduct a series of experiments with its functional counterpart, which has been known for decades. It is like an emulator on slow hardware: and there are no real quantum effects, and the performance is not the same. But the IAC is similar, as well as the behavior of the device in the circuit.
From the VAC, we can conclude that the analog is a bipolar with some uncomplicated circuitry inside. Here it is :
Experiments with a tunnel diode analog
The author tried 2N3904 and 2N2222 transistors, but it turned out that 2N4401 works better. The properties of the analog can be varied by selecting the resistor R6. The circuit of the improvised characterizer is still the same :
Experiments with a tunnel diode analog
And it still measures on one channel the total voltage on the "diode" and the resistor, and on the other channel only on the resistor. The voltage drop on the "diode" only can be determined by subtraction. And knowing the voltage on the resistor, you can calculate the current.
The characteristic works the same way regardless of the form of oscillations produced by the oscillator. The frequency of the author has set the frequency to about 100 Hz. Analogue is much stronger than real tunnel diode: you can not be afraid to put it out of operation by static, slightly over-voltage from the generator, too long soldering. The characteristic is as follows:
Experiments with a tunnel diode analog
The negative resistance on that nearly linear portion of the VAC where it is present (from 1.55 to 3.0 V) is approximately -64 ohms. The current drops from 27.2 to 4.4 mA as the voltage increases in this range. As the voltage increases further, the current increases slightly.
Analogous tunnel diode oscillator is obtained by simply including an oscillating circuit in series with it and supplying power :
Experiments with a tunnel diode analog
The calculated frequency is 5.033 kHz, the real frequency is 5.11 kHz. The generator works in the range of supply voltages from 1.6 to 3.6 V, the best form of oscillation is obtained at 3.6 V. But at voltages higher than 2.6 V the generator does not self-start, that is, you must first start it at a lower voltage, which then gradually increase to the optimum. The oscillation amplitude is greater than the supply voltage: at 3.5 V it is 4.3 V.
Experiments with a tunnel diode analog
A capacitor in parallel to the power supply is not necessary at this low frequency.
The tunnel diode analog voltage amplifier is quite unusual: it is powered by the amplified signal and the amplitude at the output is slightly greater than at the input. To get such an amplifier, just add two resistors to the device: 51-ohm resistor reduces the output resistance of the oscillator to 25 ohms, 30-ohm resistor is a load resistor:
Experiments with a tunnel diode analog
We apply rectangular pulses, adjust the amplitude, and suddenly we see :
Experiments with a tunnel diode analog
The amplitude at the input is 1.26 V, the output is 1.84 V.
Of course, no miracle happened, the author added to the input signal and adjusted some "offset". Apparently, the oscillator he has has a function to shift the signal up by adding a constant component to it. Due to this the output amplitude is greater than the input, although the circuit does not have any capacitance and inductance, except for the parasitic ones. But the amplification of the AC component is evident.