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# flippityflop

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2. ## the finer points of electronics - II

so it's Ve = Vc - Vbe? ok... i missed that from just reading from wikipedia... i read the voltage on the load is *mostly* is constant for most of the operating current range... then again the examples from wikipedia has the load on the collector side... collector side, then...
3. ## the finer points of electronics - II

well, emitter in saturations is still slightly bit higher... (Ie_sat = Ib_sat * (1 + hfe))
4. ## the finer points of electronics - II

answering my own question again: it just struck me, but maybe the capacitor was not charging not because of properties of currents in collector and emitter for any NPN, but because i've been thinking in terms of conventional current... Let: Q be a sub-circuit of an avalanching transistor and capacitor in parallel. in my case, the avalanching transistor is 2N2222; the "generic NPN" is not the 2N2222 mentioned. whenever Q was in the emitter side of the generic NPN, the negative terminal of the Q's capacitor is already in the highest negative charge. the momentary opening of the generic NPN's collector applies a "more electropositive voltage" to the capacitor's positive terminal, but there are no charge carriers migrating to said terminal. hence when the generic NPN stops conducting, the "more electropositive charge" is not held. if we were to put Q on the collector side, the positive terminal of its capacitor is always what it is supplied to it. when the generic NPN starts conducting, electrons rush to the negative terminal of Q's capacitor and when NPN stops conducting, the electrons stay there. hence, we have negative charge there. is this correct? i'd appreciate it if somebody would confirm this.
5. ## the finer points of electronics - II

i'll solve the specific circuit problem on my own... although, i would like an answer on the first question... when switching, is it better to go with the emitter on NPNs and the collector on PNPs?? do their electrical characteristics differ more than slightly higher currents?
6. ## the finer points of electronics - II

i'm asking as i've been working on a design that to my understanding should've worked. i have a generic NPN restoring the supply voltage and feeding it's emitter output to a 2N2222 parallel to a charging capacitor for a delayed avalanche. somehow the avalanching only works when i swap the 2N2222 + charging capacitor sub-circuit to the collector side. it surprised me as when it was connected to emitter, it was also directly connected to ground. and when it was on the the collector side it was directly connected to the supply. so it was not isolated and would be biased to a common ground. although, as a side note, when it was on the emitter side, the charging capacitor might have caused a reverse current through the generic NPN and leaking to other parts of the circuit. so i probably should've put a diode in there. well i didn't get the chance to as i blew my 2N2222, so now i have to go to my local supplier to have more. so i'm not completely sure what to make of it... EDIT: the generic NPN is "on" strictly less than the time needed by the 2N2222-capacitor sub-circuit to avalanche.
7. ## the finer points of electronics - II

alright, continuing the series... another question i would like to as is on NPN BJTs, would it be better to put the load on the collector side or the emitter side?? in schematics, i almost always see it on the collector side (Ic = hfe * Ib), but the emitter side also works and when doing plain switching (in saturation) the emitter side works at least as well (Ie = Ib * (1 + hfe))... so would there be any difference? the same with PNPs, when it comes to switching, would the collector side (Ic = Ib * (1 + hfe)) work better than the emitter?
8. ## are BT2222 transistors the same as 2N2222

awesome! thnx.
9. ## minimum reliable low currents

i need to know what is the lowest current that is reliable for cases such as: a.) charging a capacitor b.) when the current is being read by an instrument such as an ammeter c.) logic signals what i mean is that even outside normal conditions -- exposed to hot summers and cold winters, being touched by bare hands when testing, or when it's humid, etc -- what are the minimum low currents that will cover a, b, c above?
10. ## are BT2222 transistors the same as 2N2222

are these NPN BJTs: http://pdf1.alldatasheet.com/datasheet-pdf/view/17918/PHILIPS/MMBT2222A.html the same as those 2N2222 that has been around for since forever? can i trust that the reverse active and avalanche breakdown profiles are the same??
11. ## comparator for DC voltage

ok i actually just realized the flaw after i last posted. i thought of mentioning it, but i thought it will have you guys think that i am trolling. (i actually just checked again for additional posts from you guys) yes, hero999 there needs to be a common ground here for this to be a universally applicable (aside from the aforementioned caveat that you have to balance the R1 and R2). to see why, we need to visit what was posted in this thread (hence my fear of this being seen as trolling): http://www.electronics-lab.com/forum/index.php?topic=39704.0 basically, V1 and V2 are just voltage drops, but the actual voltage potential of both grounds of V1 and V2 may be different (can be taken by using a third reference voltage or if you want to be absolute, the negative elementary charge). so in actuality: |V3| = (V_ref_pos1 - V_ref_gnd2) - (V_ref_gnd1 - V_ref_gnd2) if V_ref_gnd1 >= V_ref_gnd2 or (V_ref_gnd2 - V_ref_gnd1) - (V_ref_pos2 - V_ref_gnd1) if V_ref_gnd1 < V_ref_gnd2 notice that (V1 = V_ref_pos1 - V_ref_gnd1) need not be greater than (V2 = V_ref_pos2 - V_ref_gnd2) to have a positive V3 = V1 - V2, the opposite can actually happen. it really is dependent on the relationship of V_ref_gnd1 to V_ref_gnd2. anyways, this can be further compactified as: |V3| = | (V_ref_pos1 - V_ref_uni_gnd) - (V_ref_pos2 - V_ref_uni_gnd) | where V_ref_uni_ground = min(V_ref_gnd1, V_ref_gnd2), which is obviously the offset or translation along the x axis our values. but if we allow V_ref_gnd1 = V_ref_gnd2 = 0V, then we simply have |V3| = | V1 - V2 | as for my part on drawing 2 independent voltage sources, i was trying to be general. but, i probably should've explained or added after i realized it; that we still need a common ground. of course, we can't simply add a shorting wire on both grounds of V1 and V2, as that would bypass the V3 path. a high resistance short also would not work, basically you just have another non-functioning comparator. what we can do is ALSO have V1 and V2 be sourced from another common voltage source V0, so practically they are biased in a V_ref_uni_gnd which is V_ref_gnd0 from either a single V0 or if you have several individual sources, their grounds must be shorted.
12. ## RF - separate transmitter and transceiver antennas for half duplex

i was wondering why is it, for just half duplex systems, don't we have a dedicated transceiver and a dedicated transmitter antenna. ok, just hear me out... assuming we are using grounded monopoles, we can have a resonator connected to a diode whose anode is connected to the transmitting antenna, and have a receiving second antenna connected to the cathode of another diode then going to the resonator. the transmitting and receiving antennas would also be made of different materials that are nonreciprocal. ferrites that are biased to transmitting and receiving (higher gains). since they're half duplex, we don't even have to have 2 different resonator circuits. so basically, if this is feasible, we don't have to change anything in the current systems, just plug in these dedicated antennas... am i wrong here?? also, why do we not have a "Radio" section?? i think it warrants one.
13. ## comparator for DC voltage

you know what i'm talkin' about... anyways, just in case somebody stumbles upon this simple thread in the future, i'll attach a more concise diagram:
14. ## the finer points of electronics - I

also, why i am convinced that sometimes it might be helpful to consider "pulls" is that i see a lot of voltage supplies apparently provides negative voltages.
15. ## the finer points of electronics - I

ok, i guess i lose here... in all cases "conventional current" and the idea of 0V grounding that comes with it abstracts all cases when it comes to passive components. in active components as long as it is only immediately in series with a passive component, then it *should be safe*. if 2 or more active components are in series, then i'd still raise questions if it could work. ok, look at the attached diagram and apply conventional current and see if we can make it all work. suppose the 2 identical avalanche diodes in series with a active component "Q". we also define an "ambient" voltage potential in the non affected/conducting components such as leads, and wires, any conductors. the voltage drop from each end, is of course, the whole voltage applied to the circuit. the voltage potential from the left of "D_av1", is say, 3V above ambient. the voltage potential from the right of "D_av2" is -4V below ambient. that's a voltage supply of 7V. say the avalanche diodes have a breakdown at 5.5V across. how this would *usually* work is when we have *single active component* with at least 2 leads and have their electric potential on their immediate 2 leads interact, either by voltage potentials and/or current created... so simply as connecting a single 5.5V avalanche diode to a 7V will be enough to have avalanche breakdown. this is the same for all passive components -- resistors, inductors and capacitors. but what will happen if we cannot continuously pass the voltage potential all the way from the other end of the circuit to make them interact in any components?? such is the case when we have Q as a hypothetical active component that DOES NOT maintain voltage potential across it the way passive components do. the voltage across D_av1 is only 3V. and, Q is not letting it's left lead have a voltage potential negative from ambient. the same would be true for D_av2, it only has 4 volts across it and "Q" will not let it's right lead have a positive potential from ambient. of course, this is hypothetical, as i don't know of a Q component that fits what i'm describing.
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