TheTaoOfPhil
- Mar 10, 2013
- 3
- Joined
- Mar 10, 2013
- Messages
- 3
Hi,
I am working with several different electronics books to understand the basics of NPN transistors. The only discussion that I can make sense out of is that of Delton Horn, Basic Electronics Theory, pp. 278ff. Since this book is notoriously replete with errors, I want to make sure that what I'm taking away from his discussion is accurate.
I am including a diagram of the NPN configuration addressed by his common-emitter example. From his discussion, it seems that:
1) As per the voltage divider R1, R2, and R3, the voltage levels seen by the collector, base, and emitter must descend in polarity respectively. In other words, the collector voltage must be greater than the base voltage which must be greater than the emitter voltage. Other authors focus on the base-emitter polarity only.
2) The AC signal is applied to the base on top of this arrangement for biasing. That is, the DC bias maintains the emitter-collector flow, but the signal level at the base relative to emitter ground drives the amplified output at the collector.
Is all of this correct?
Final question: He says that R3 is necessary to drop the voltage seen by the emitter to below that of the base. The implication is that the emitter sees the ground to which R3 is connected. However, according to the schematic, the battery is also connected to ground. Shouldn't R3 be directly wired to the emitter so that the emitter sees it instead of seeing the battery ground? (I'm sure my question is wildly naive, but this is how one learns )
Many thanks!
--Phil
I am working with several different electronics books to understand the basics of NPN transistors. The only discussion that I can make sense out of is that of Delton Horn, Basic Electronics Theory, pp. 278ff. Since this book is notoriously replete with errors, I want to make sure that what I'm taking away from his discussion is accurate.
I am including a diagram of the NPN configuration addressed by his common-emitter example. From his discussion, it seems that:
1) As per the voltage divider R1, R2, and R3, the voltage levels seen by the collector, base, and emitter must descend in polarity respectively. In other words, the collector voltage must be greater than the base voltage which must be greater than the emitter voltage. Other authors focus on the base-emitter polarity only.
2) The AC signal is applied to the base on top of this arrangement for biasing. That is, the DC bias maintains the emitter-collector flow, but the signal level at the base relative to emitter ground drives the amplified output at the collector.
Is all of this correct?
Final question: He says that R3 is necessary to drop the voltage seen by the emitter to below that of the base. The implication is that the emitter sees the ground to which R3 is connected. However, according to the schematic, the battery is also connected to ground. Shouldn't R3 be directly wired to the emitter so that the emitter sees it instead of seeing the battery ground? (I'm sure my question is wildly naive, but this is how one learns )
Many thanks!
--Phil
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