... why Q343 have a net connects to 0V?
Which means, the main current goes directly from +5V to -5V , apart from a small part which goes directly from +5V to GND, the latter one through Q313 , several current sources and resistors. Hence the main current goes through the transistors Q1 .. Q4 , and Q321 & Q343 . Check all these currents uniquely!Hi erikl: the current between GND and netC is a little bit smaller than the current between GND and VDD(5V)
Yes, I thought so. Don't be irritated by my two Co_sub connections in your image: I know they go to different BND isolation implants of different transistors.In fact, the cross-section image of Q343 shows three PNP transistor, i.e. there have three PNP transistor, whose collector, base & emitter contacts together.
I do analyze the circuit by simulation, and I don't think the simulation is useful. From simulation, Q1~Q4 have no current, the current of Q321 and Q343 is only 80mA. But from testing result, the current is so big!!
... from the testing result I think there have big current from Co_sub to the collector of Q343 (but the current should never existed!! because the Co_sub and collector of Q343 is a reverse diode).
I don't know if my ideal is right or not, so help me please, thanx!!
Try if there is a meaningful current rise when you slowly increase the voltage between Co_sub and Sub - if you have access to Co_sub. If so, this would mean a rather low reverse breakdown voltage between the BND and Psub junction (which is not usual).- - - Updated - - -
Again: How can I get rid of the reverse saturation current Is by layout?
Then I'd think Q2 & Q4 are nothing else than the BP-BND-Psub parasitic PNP transistors below their upper PNPs. And they should anyway be depicted like your Q0 (collector Psub has the lowest doping concentration, emitter BP the highest).from the foundry process datasheet, the size of Q2 &Q4 can not be reduced any more.
Right; but don't connect to Sub, as shown in the Q0 figure (= Psub , according to your first figure above), because this is the most negative voltage. I think you should connect it to the collectors of Q1 (net N1) respectively of Q3 (net N2). And right: as many metal connections as possible.Maybe the only thing I can do is more connections between Co_sub and metel one in the layout to reduce R0.
In this part of your circuit I think the reason for the meaningful current rise is just the non-negligible current gain of Q343.For the transistor Q321, I can't access Co_sub, but I can disconncet all connections of Co_sub, at the same time, I can slowly increase the voltage of the Collector from 0V to -5V, there is a meaningful current rise, I think this phenomenon can also means a rather low reverse breakdown voltage between the BND and Psub junction.
Of course there are unavoidable parasitic PNP transistors like Q2 & Q4 (which I think should be replaced by a reversed circuit like Q0) each as large as the overlying triple PNPs. You need to characterize them as PNPs with relatively low current gain, and you know their area. Would be good, if you could get hold of doping concentrations and thicknesses of their layers.Finally, do you mean that my ideal is not correct enough and there have no parasitic bipolor Q0? thanx!!!
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