I'm pretty new to all of this and I've learned a lot in the last couple of months, but I know many of you have been in this hobby for many years and I was hoping someone with a bit more experience could speak to the efficiency of common emitters?

I have a Noctigon KR4 and I'm so surprised by how quickly this thing gets HOT hot, like too-hot-to-touch hot. I know there is a disclaimer on the product page stating this, but I was surprised how quickly this thing heats up and starts ramping down due to temp. I have it properly calibrated and it seems to step down from turbo in about 25 seconds.

I have a tint ramping version with SST-20 4000K and XP-L HI 6500K. Did I just happen to choose two very inefficient emitters? BTW I ordered this after independently researching the emitters without considering how they would compliment each other... each on their own are nice but they're a couple of floody emitters with different color temps, meh. Not too useful. I've got a better flood/throw combo on the way :)

So I guess these are my questions: what do you consider the most efficient emitter to be? If you were buying a tint ramping model, which two would you choose for efficiency's sake? Are you willing to sacrifice efficiency for color temperature and beam properties?

TIA, this community has been most welcoming

I breadboarded a basic common emitter amplifier boost circuit with a germanium transistor and I'm getting a little bit of dirt. I'm happy with it because it is ideal and pretty close to the tone I was looking for, It is really warm and the clipping is subtle but rough if that makes any sense. I think I messed up the biasing and I'm getting some asymetrical clipping because of it but I could be wrong. I am just asking because I don't know if some clipping is normal or not and I would like to improve my future gain stages. I am new to circuit design and making pedals in general so anything helps.

In LTSpice.I set up a npn linear amplifier.Changed the npn parameter "Bf" from 100 to 200.

I thought Bf was Beta. The common emitter current gain of the BJT

[following ie = ic + ib, and ib = ic/Beta, and no early effect] I thought doubling Beta would half the base current (ib).

I'm barely measuring a change. Idkw

https://imgur.com/a/gdDyHME

Edit: So at Beta = 100. Everything lines up. ib = .023 and ic = 2.3, Then at Beta = 200 I get ib = .023 and ic = 3.3.?

Oh

it must be a saturation issue

i guess

because Vce goes low

Hi!

I've been studying BJTs recently and some things are confusing me a bit, so I have four questions.

1. The book I'm studying from presents a relationship between VBE and IB, which makes sense. Later on, it presents a connection between IC and IB, which also makes sense. The only thing that bothers me a bit, it's not explained exactly how BJT regulates current. I'm assuming it changes VCE voltage drop according to the IB, but I'd just like a confirmation or if I understood something wrong, a better explanation.
2. When using BJT as a switch, the configuration stays identical, it's only the way we "look at it" that changes the behavior? By this, I mean, in the amplifier case, we're actually amplifying input VBE voltage which then changes IB, which affects IC, which should affect voltage drop on a resistor in the outer circuit. In case of a switch, we're just changing VBE from some value to zero so it switches the outer circuit on or off?
3. Why is the dynamic input resistance calculated as a difference in VBE and IB? Does this mean if we put an AC source in the input, it will cycle between different points, so we take an average and say that's DC resistance, or is there any other reason?
4. In the common emitter amplifier, why are we filtering out the DC component? Would it be possible to amplify DC signal with a BJT? Would a regular switch configuration actually act as a DC amplifier?
5. In common emitter amplifier, there is a capacitor connected to the ground from the emitter node (CE). It's not the capacitor that filters input voltage DC component, nor is it the one doing it on the output. What's it's purpose? The tutorial says it acts as open loop for DC component, but can act as a short circuit on extremely high frequencies. Both of these make sense, but I still don't understand what its purpose is.

Thanks for your time, and have a nice day!

Hi, so Ive designed a common emitter amplifier in Multisim and without a load resistance the circuit works fine and provides a gain of 16. However, when I add a load resistance of 50Ohms instead of amplifiying the signal it gets reduced (as you see on the photo provided)

What should I change to make the gain the same as without the load and why does this happen?

Thanks!

P.S.: Im a first year electronic engineering student so Im still know the basics.

https://preview.redd.it/k33wpoa7kqs61.png?width=1223&format=png&auto=webp&s=06ea8d5cde3741fe8a5b992796b0336a37632a74

Help me out I can't find where I can get something like a step-by-step manual on how to design a common emitter amplifier. My teacher kind of forgot to teach me how to design one of those I guess, and now I have a report to write on this.

Hi, Does anyone have a pdf or anything that can explain exactly how does resistors an capacitors work in common emitter amplifier circuit? I kind of know that 2 resistor are voltage dividers and capacitors are vor bypassing AC. But i don't fully understand what this means...

Hi all, I've been learning LTSpice recently and needed to simulate a basic collector biased common emitter amplifier. Doing an AC sweep for input impedance returned numbers as high as 1.6TΩ which obviously isn't right. Any ideas what I might be doing wrong? Here is a screenshot of my circuit and simulation. Thanks

I read somewhere that DC and AC should not be connected in parallel.

Question #1
In below common emitter circuit is Vin parallel to Vcc?

Question #2
Assuming C1 is not there (blocker for DC circuit),
Vcc = 5V
R1 = R2 = 10K
Voltage divider value at R1 and R2 is 2.5V
What should be Vin range assuming peak voltage of 1V:

a) 2.5V +- 1V ( 1.5V - 2.5V - 3.V)

b) 0 +- 1V (-1V - 0V - 1V)

I am trying to understand if A/C voltage source has to match voltage divider voltage which is 2.5V in our example.

https://preview.redd.it/hkw1e0q75e451.png?width=649&format=png&auto=webp&s=fdb5e514f770122077780f0ed635a2c27564cb13

I put together a basic common emitter amplifier, after watching a number of videos, reading a few books, etc. I ended up cobbling together an amplifier that gives me ~10dB gain, based on the 2n2222 transistor (of which I have plenty lying around).

One thing I noticed while playing around with it was that if I added a (fairly large) inductor in series with the collector resistor, my power doubled. I am testing with an injected signal of 2MHz, and powering the circuit with my linear benchtop supply. I'm measuring power using my oscilloscope, calculating it from the voltage across R5.

Please view the circuit diagram at the link below.

https://imgur.com/a/eMRzm5m

Why does L1 double power delivery to the load in this circuit?

Thanks for any help you can offer!

What equation would I use for band passing frequency for a common emitter BJT. I am trying to have it pass 1kHz-20kHz, but i don’t know how to calculate what capacitor and resistor values to use for the input capacitor, the emitter capacitor, and the capacitor that links the emitter to the collector (npn).

When I first started watching (and later reading) BNHA, I thought it was just coincidence that there were several students with direct drawback from overusing their quirks. I chalked it up to something common to most if not all quirks, noting that some students and all the pros have no issue simply because they had better quirks or were more used to them.

However, all the most notable examples of a quirk having a direct physical toll from overuse (with the exception of Mineta) are emitter quirks; besides him, transformation and mutant quirks seemingly never cause the user to feel nauseous or exhausted, more importantly, every time that those do cause physical harm its the direct result of how the quirk physically works rather than the quirk factor itself apparently causing the damage. I didn't properly notice this until much later, and I never took the time to look into it until now...

A very important indication that my line of thinking about how quirks generally worked with drawbacks was how the best students handled their emitter quirks; Bakugo, Todoroki, and Momo all have pretty drastically different quirks, methods of usage, and ways of dealing with the drawback. A naive assumption would be that Bakugo and Todoroki's quirks only have direct physical drawbacks, after all, Bakugo does have to deal with recoil and Todoroki has to manage his temperature; but behind the scenes we can see something very different happening, Bakugo is directly limited and weakened by production of explosive sweat and igniting it, he's come to manage it but its very clear that he has a limit as to how much his quirk factor is able to work up the power and amount of sweat... Given that he has no mutation to sweat harder, the only thing we can assume would be the actual application of his quirk factor would be in making it explosive and how explosive he can make it, combined this puts a very high wall for Bakugo to surpass with his quirk; its a huge weakness to have to manage all this whilst presumably a mutant with a similar quirk wouldn't have such issues (sweat production and explosivity would be from the same source). As for Todoroki, one might assume that his drawback comes primarily from the physical stress of the temperatures; but Bakugo (likely speaking from his experience as well as knowledge) corrects that and says his quirk factor works like two mana bars that refill eachother. I think that this is a VERY interesting situation and its apparently the only emitter

Hi guys, I am learning, so, if you will spank me, do it softly...

I am trying to design a common-emitter amplifier just for the whole purpose of learning.

Can you guys see if the calculations I have done are correct and help me calculate the input/output coupling capacitors?

The circuit will be like this

I have chosen the following values: Vcc = 18, Ic = 8mA, transistor 2N2222A.

hfe for that current is 225, according to this: http://web.mit.edu/6.101/www/reference/2N2222A.pdf

I have chosen Ve to be 1V.

Vce minimum is chosen to be 2V. I see it is not good to have a Vce lower than that.

If Vce minimum = 2V, them Vc minimum = Vcemin + Ve = 2 + 1 = 3V

So, the output may swing from 3 to 18 V, right?

The middle of this range is 10.5V. So I have designed Vc to be sitting at 10.5V.

For maximum output,

================= CALCULATING RE

ie = ic + ib ie = 8mA + 8mA/225 ie = 8.0355 mA

if Ve = 1 and Ve = Re.ie then

Re = 1/8.0355mA = 124.44 Ω

================= CALCULATING RC

If Vc is set at 10.5V and Vcc is 18V, Rc should produce a voltage drop of

18 - 10.5 = 7.5V

so,

Vrc = 7.5 = Rc.ic 7.5 = Rc(8mA) Rc = 937.5 Ω

================= CALCULATING R1 and R2

To make the circuit stable I choose i1 to be 10% of iC so, i1 = 10% of 8ma = 800 uA.

if Ve = 1 and Vbe = 0.7V, then Vb = 1.7V

i2 = i1 - ib

R2.i2 = Vb R2 (i1 - ib) = Vb R2 = Vb/(i1 - ib)

R2 = 1.7/(800uA - 35.55uA) R2 = 2223 Ω

R1 = (Vcc - Vb)/i1 R1 = (18 - 1.7)/800uA R1 = 20,375 Ω

================= CALCULATING Cin

First I calculate the input impedance that, as far as I know is equal to

Zin = R1 // R2 // (rπ + Re(hfe + 1))

rπ = kT/qib = 26mV/35.55uA rπ = 727.09 Ω

So, Zin = 20,375 // 2223 // 727.09 Zin = 1874 Ω

As far As I have researched, Cin is calculated to have a reactance equal to 2/3 of Zin at the cut frequency. Suppose 20Hz.

Xc = 2/3 of Zin = 1249 Ω

So

Cin = 1/2πfXc Cin = 1/2π(20)(1249) Cin = 6.36uF

Now I don't know how to calculate Cout. Suppose the collector will drive a 600Ω load (high impedance headphone).

Two questions:

1. are my calculations correct?
2. how do I calculate Zout and consequently Cout, to be connected at the col