Transistor biasing

Your signal source interferes with your attempt to bias transistor base. It's a very low output impedance signal generator, therefore "stronger" than your bias voltage. I've added a resistor between signal and base here: http://everycircuit.com/circuit/6471433017098240

Right @Bushmills, this strong generator will also clamp the DC. Which is actually the BiasPoint. To decouple and be free to make your choice with e.g. 100kOhm you can use a capacitor. Working resistor must also fit the abilities in gain of the little trransistor and 50Ω against 10V is to heavy. 500Ω is ok. http://everycircuit.com/circuit/5187050628972544

@Bushmills, yours can be identical with just 350mVp AC input instead 1Vp when DC is aligned ;) nothing else changed http://everycircuit.com/circuit/6173262294548480

With all resistor values changed, I thought I'd keep at least signal generator settings as they were :) added scope trace on base shows the offsetting from the symmetric signal generator source.

jaja

Joh abba äschd

Thanks for your help :-) next question, @Bushmills, why is the signal inverted? Sorry for my newbie questions, I'm trying to learn :-)

Because the scope trace shows voltage at collector of transistor, not current into it. When base is driven, transistor opens, therefore voltage at collector drops.

Tap resistor at collector, then tap the "eye" icon, to see current.

Ah now I see, thanks! :-)

@Bushmills, for me the volmeter shows correct. the top pin is +. Anyway, you never know which polarity the voltmeter uses. So better dont use them as beginner and highlight the wire/node/trace directly and watch it on the scope. But maybe the question was, why is input base to collector in principle inverted? In common emitter circuit as class A amplifier the collector voltage is inverse (in most situations) to the base voltage/current, but why? BTW, Its always better to talk about currents when talking about BJTs. Thats not easy for a newbie but will help you a lot in near future! @Bushmills? söjbs shujd !

I wish I could remember what I found most intuitive when I struggled do get this into my head - but by now I like to think in terms of voltages - that's after all what a component connected to C "sees", making the mental step to convert from convenience current to more practical voltage unnecessary. The voltmeter I've btw removed from the version burgerkalif probably refers to, I don't find them very useful, they just clutter breadboard space and reduce remaining real estate. As you ask why there's an apparent 180° phase shift between U and I - well, think of a light switch instead of a BJT, and an incandescent lamp instead of the R, then measure voltage across the switch. You can now easily see that it drops to almost zero when I through lamp rises as result of closing the switch. But when measuring across the lamp, U and I are in phase again. Kahine uhörzarre.

Right, i myself remember and as beginner 45years ago i was C'ing circuits only from Voltages point of view, current at second priority. Let me explain why this is stupid and a longer brain way to think about those circuits. You are allowed to use a switch as picture for a BJT collector-emitter raceway. YES, But you noticed how you struggled to avoid the word current to explain the inverting behaviour only in voltage language? Read again and give the word current a better chance. Read maybe twice or even more. You will see how easy life can be when talking about the think we have and not whats the root cause (voltage) what we had in the step/past before and now is not from first priority. Remember, Voltage is the root cause for current! First you need some electrons to put somewhere, then you can close the switch and the electrons will run, !current! I really hope you all understand now better! tu mischt uchbarben un scheibst lügwörz? Sauh shwör su lehschen. Mah ma eywacherr

Ehm no, I didn't struggle at all to avoid the word "current". I wasn't even aware of not having used it, until you mentioned so. You probably look at where I said "voltage over lamp" rather than "current through lamp" - as you correctly observe, voltage (or rather, potential differential) is the cause for current. Some may now prefer to look at causes, others are happy with effects. I find that considering the cause of an effect helps me to gain a better understanding than looking at the effect without consideration of the cause. Though, as you correctly observe again, the latter may make life easier. At least until one wants to connect an output (used to sink some current) to what serves as input of another stage, and finding that the input doesn't really care about the sunk current. It cares instead about the voltage (which may, again, result in a larger or smaller current) towards the input). Unn auno midd Gäh-schahrchdelde glommere, risch-disch räh gur sief.

To try to keep the help a little bit simple for beginners, try; http://everycircuit.com/circuit/6593152390266880 try altering the values of each component (just a little bit), see what happens.