Dear Itsu,
IMHO, when negative resistance manifests in the V - I characteristic curve of a two terminal device by biasing it within a certain voltage - current range from an outside source like a battery, (see Naudin
http://bingofuel.online.fr/cnr/images/negosndr.gif ) then this device cannot "produce" higher output power than what its DC input bias provides. This is valid for both kinds of devices I mentioned in my previous post i.e. for 2 terminal devices like tunnel and Lambda diodes, reverse biased pn junctions etc and for 3 terminal devices like bipolar and field effect transistors used in circuits where positive feedback is intentionally created by appropiate components to create negative resistance between two terminals of the 3 terminal device.
Regarding the brightness of the input and output bulbs: In Nelson's videos, if the input bulb is the one labeled as E1 in his original schematic, then its brightness refers to how much power the bulb consumes, in series with the circuit, nothing else. This bulb acts in the circuit as the upper member of a voltage divider and the lower member of this divider is the rest of the circuit, ok? Power levels consumed are different for the two because the voltage levels are different across them while the current is the same.
I understand that the output current (38.8 mA) is higher than the input current (which is between 20 and 30 mA) as measured in video 2 for instance. The input voltage is 24 V as shown but I do not know the output voltage level across the bulb E2 if that is assigned for the output load.
Nelson mentioned in video 1 the bulbs are 12 V 1W rated bulbs with 6 Ohm cold resistance. This means that almost the full 24 V feeds the circuit (E1 bulb in series with the input remains dark because it has no enough voltage remaining from the rest of the circuit) and E2 output bulb may get roughly 8-10 V output voltage to have the brightness shown (it is a 12 V bulb).
I understand that you wish to see similar behaviour in your replicated circuit (for instance see the difference in the two currents).
It is possible that with MJE18008 transistor you get closer to those values. With oscillators it is a bit difficult to deal with to make them operate similarly. Sorry that changing R1 in the simulation circuit did not have any effect (what I expected).
Regarding C3 in Nelson's circuit (C1 in yours) I still think it establishes positive feedback from collector to emitter (but only in case R1, the bulb in Nelson circuit has at least 6 Ohm or higher value) and as a feedback capacitor it surely influences operating frequency too but in a smaller extent than a real tuning capacitor would do say in parallel with the coil L1.
If you vary C4 10 nF in Nelson circuit, does it change frequency better than C3 (i.e. your C1) ? Try to vary it if you have not done it yet.
Regarding the roughly 3 times as high input current, does the 300 Ohm resistor in series with the base in Nelson circuit (you show a variable potmeter in the sim) influences input current much? If you put say a 470 Ohm potmeter in your real circuit, would input current change by varying the pot?
What is not ok in the sim is you had to remove the coupling factor between L2-L3: can power be transformed to the output with zero coupling? Or how the heavy load of R2, 10 Ohm (if you meant that) could appear for the oscillator with zero coupling for L2-L3?
Regards
Gyula
Author
Topic: Itsu's workbench / placeholder. (Read 137213 times)
