Common Collector Amplifier

[Chryseus]

Hi, I've been studying electronics for quite some time and now have started actually building electronic circuits.
This is the first common collector amplifier I have built, and would be very grateful if anyone could check over my measurements, and the equations I have used.

In particular I want to make sure I got the input and output impedance right.
I have attached the schematic and the PDF containing all my measurements.

The transistor data sheet can be found at: https://www.electro-tech-online.com/custompdfs/2010/03/296667.pdf

I'm currently reading Art of Electronics and the impedance equations on page 66 seem to make little sense to me, mathematics is not my strong point

 

[crutschow]

Don't understand your resistor symbols with a angled arrow at one side. Are those supposed to be potentiometers?

 

[Nigel Goodwin]

Don't understand your resistor symbols with a angled arrow at one side. Are those supposed to be potentiometers?

Yes they are pots, the entire thing seems very bizarre?.

 

[Hero999]

Please don't post weird circuits.

 

[Chryseus]

errrm... Potentiometers have three terminals, two on each side and one on top, the symbols used are the British symbols rather than the American ones.
Needless to say in this circuit they act as variable resistors.

 

[Hero999]

It's not normal to use an angled arrow for a pot. but that doesn't bother me or Nigel.

Where's the input and output?

Is this a school assignment because it looks like it has no practical purpose?

It's an emitter follower rather than a common emitter amplifier.

I real common emitter amplifier has a collector resistor with a lower value (or no) emitter resistor which is in some cases bypassed by a capacitor.

The base impedance is equal to the gain multiplied by R2. The base voltage can be calculated using the potential divider formula. The emitter voltage will be equal to the base voltage minus one diode drop.

 

[Chryseus]

This is not a school assignment and I'm aware it is an emitter follower.
I noticed that I calculated the input impedance wrongly, it should be 15.701kΩ rather than 89Ω
and the output impedance is about 1Ω with the equation R2 * Rs / β where Rs is the source impedance.

 

[Jony130]

BJT equation for CC amplifier.
Ic=Ib*β
Ie=Ib+Ic=Ib*(β+1)
and
β=Ic/Ib

Vb=Vbe+Ie*R2

Zin=(β+1)*(re+R2)
Zout=R2||( re + (R1/(β+1)) )

 

[crutschow]

It's an emitter follower rather than a common emitter amplifier.

He stated it was a common collector circuit which is an emitter follower.

 

[Hero999]

Yes, you're right, I'm not used to the term common collector amplifier but you're right, it's the same thing as an emitter follower.

 

[kinarfi]

I hate to be critical, but I see a lot of narrow mindedness on the forum. May I suggest that every one just try to be helpful, instead of trying to make everyone conform to a their method of diagramming, drawings, and schematics. I have never seen this particular potentiometer diagram, but it was instantly recognizable as such. I have had problems with others accepting some of my drawings also. But I just wanted some help, not drawing lessons. Open your minds and learn that there are as many ways to draw things as there are people.
Kinarfi

 

[Vizier87]

that's bold. But I'll put it this way: I'm not gonna mess with our gurus here!! *cowering*

 

[ericgibbs]

I hate to be critical, but I see a lot of narrow mindedness on the forum. May I suggest that every one just try to be helpful, instead of trying to make everyone conform to a their method of diagramming, drawings, and schematics. I have never seen this particular potentiometer diagram, but it was instantly recognizable as such. I have had problems with others accepting some of my drawings also. But I just wanted some help, not drawing lessons. Open your minds and learn that there are as many ways to draw things as there are people.
Kinarfi

hi kinarfi,
I will support that comment.

The OP did at least produce a circuit diagram, did say he was a 'wanabee' and he ask for help regarding his equations.

I have often seen arrowed potentiometers drawn that way, it obvious what was meant.
Also he did say Schottky in his post title.

 

[kinarfi]

Thank Eric and my apologies to Chryseus for the hyjack
Kinarfi

 

[Jony130]

In Europe this is a standard diagram symbol for potentiometer.
Potentiometer - Wikipedia, the free encyclopedia
**broken link removed**

 

[Hero999]

I use European symbols for everything except logic gates which I prefer US symbols for because they're easier to read.

It's personal preference I suppose. I don't care if someone uses US resistor and capacitor symbols and European logic gates as long as I can read the schematic.

The only types of schematics I don't like are electrical with all the terminal blocks and wire numbers shown and switch contacts that look like capacitors; I had to work with those for awhile and I never got used to them. I also don't like it when people draw amplifiers or logic gates as boxes because I have to keep referring to the datasheet every minute.