![]() ![]() And 0.3 V (which is half of the nominal 0.6 V bias of the BE junction) is a reasonable rule of thumb.Īs the above simulation shows, the actual values you get will vary a bit from transistor to transistor - the 2N3904 is considered a "switching" transistor with low Vce, but other transistors may have higher values. The base region shares two pn junctions, each with collector and emitter. For this reason, the collector can be pulled some way below the base, but not too much. A bipolar transistor (bipolar junction transistor: BJT) consists of the collector, base, and emitter regions, with the very thin base region located between the collector and emitter regions. Your comment earlier about throwing out good transistors because of that. Now when the collector is pulled towards the emitter, the BC junction starts to be forward biased: once that happens, it will "steal" current from the base, and less current is available to flow in the BE junction. I can happily work out whether its NPN or PNP though. Solution : Fig.1 Collector supply voltage, V CC 6 V Collector load, R C 2. (ii) The minimum zero signal collector current required. Posted about my SAB listing a few weeks ago about not showing up in search only when you entered the exact name. Find : (i) The maximum collector current that can be allowed during the application of signal for faithful amplification. The relationship is exponential - so the change in voltage needed to double the current is quite small. An npn silicon transistor has V CC 6 V and the collector load R C 2.5 k. It acts as the current source because it provides current through the base terminal. It is formed by sandwiching the layer of N-type material between two layers of P-type material. This transistor features two diodes that are connected back to back. The transistor starts to conduct when there is significant current flowing in the BE junction - because that is a (si) junction, this happens at around 0.6 V. Definition: NPN transistor is a current controlled circuit which comprises of three terminal that are emitter, base and collector. The NPN transistor features three terminals: emitter, base and collector. When I run the DC simulator, I get the following values:Īs you can see, the collector voltage is about 134 mV - well below the base voltage, which is 702 mV (and less than your "rule of thumb" of 0.3 V). Simulate this circuit – Schematic created using CircuitLab ![]() Here is a very simple transistor circuit: ![]()
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