Pulling my hair out here .... - Page 1
Forum section: electronics / beginners

author: Rtwo
author_rank: Newbie
timestamp: November 30, 2019, 09:04:43 pm
content: ... OK, I don't have much left so not reallyBut I'm certainly getting frustrated at where I'm going wrong with this common emitter amplifier circuit.12VDC powering the circuit1KHz/1V signal going into the base from a function generatorCould someone give me a clue where to start looking at why I'm just not seeing an amplified signal out?I've replaced all the components a couple of times in case I've fried them .... I'm stuck ...................HELPBreadboardInputOutput

author: StillTrying
author_rank: Super Contributor
timestamp: November 30, 2019, 09:21:39 pm
content: I can't see an obvious fault on the breadboard, are the emitter and collector inserted far enough in to the board.DCmeasurements such as checking there's some voltage across the 220R emitter resistor, and that the base is 0.6V higher than the emitter should find it!

author: silverback
author_rank: Contributor
timestamp: November 30, 2019, 09:23:40 pm
content: Cannot clearly see if the capacitor from the collector is connected to the output.

author: Rtwo
author_rank: Newbie
timestamp: November 30, 2019, 09:27:00 pm
content: Quote from: StillTrying on November 30, 2019, 09:21:39 pmthanks, I'll double check

author: Rtwo
author_rank: Newbie
timestamp: November 30, 2019, 09:27:45 pm
content: Quote from: silverback on November 30, 2019, 09:23:40 pmYeah, it definitely is - poor photo

author: nali
author_rank: Frequent Contributor
timestamp: November 30, 2019, 09:36:20 pm
content: 1nF input/output cap is too small - at 1kHz it will have an impedance of 159k so your 3k3//20k biasing resistors will squash any AC input signal. Try something in the uF range.

author: Rtwo
author_rank: Newbie
timestamp: November 30, 2019, 09:49:21 pm
content: OK thanksMore things to try tomorrow

author: andy3055
author_rank: Super Contributor
timestamp: December 01, 2019, 12:07:06 am
content: I can hardy make out the transistor orientation. But I feel your collector and the emitter is switched. I may be wrong though.Most of the resistor leads seem to be stretched all the way. Are they making proper contact in the b/board?

author: Dacke
author_rank: Regular Contributor
timestamp: December 01, 2019, 01:54:06 am
content: Just a quick thought. Some of the resistor leads are a bit long.... When you got them, did you pull them out of the adhesive tape that sticks them together or did you cut the ends of the leads off just before the tape? If it's the former, that adhesive residue can stick to the leads and cause bad connections in a breadboard.

author: not1xor1
author_rank: Frequent Contributor
timestamp: December 01, 2019, 06:56:18 am
content: Do you know what "subject" means?Please edit your thread subject

author: LateLesley
author_rank: Frequent Contributor
timestamp: December 01, 2019, 10:10:09 am
content: I'll second what silverback says. That output capacitor is not connected to the pin with the yellow wire.The output capacitor is connected at row 14 - row 13, but the pin and yellow wire are on row 12, unconnected.At least from what I can see in the pic.

author: austfox
author_rank: Regular Contributor
timestamp: December 01, 2019, 02:37:15 pm
content: I agree with Andy that you have the collector and emitter around the wrong way. Emitter (pin 3) should be going to ground, looks like it is going to 12V.

author: g0mgx
author_rank: Regular Contributor
timestamp: December 01, 2019, 03:00:33 pm
content: Looks like the output cap is connected to fresh air.I really dont like the 2 separate resistors in the same hole connecting to the base either.

author: Rtwo
author_rank: Newbie
timestamp: December 01, 2019, 06:42:55 pm
content: Plenty to look at, thanks allUnfortunately I've not had time today to look at it further.I'm now away at work until Christmas so I'll revisit it then.

author: Rigolon
author_rank: Regular Contributor
timestamp: December 03, 2019, 01:22:08 pm
content: Quote from: austfox on December 01, 2019, 02:37:15 pmTransistor seems to be OK. 2n2222a pinout is Emitter (1) - Base (2) - Collector (3).Emitter will be pin 3 with the p2n2222a (PNP transistor)But I agree that output capacitor is not connected with yellow wire and test pin. That should be your problem, and I didn't do the math but double check if you are biasing your transistor correctly.

author: austfox
author_rank: Regular Contributor
timestamp: December 04, 2019, 08:10:24 am
content: Quote from: Rigolon on December 03, 2019, 01:22:08 pmOops, I was indeed looking at the P2N2222A datasheet. It seems both are NPN transistors. To cause even more confusion, at least one retailer is linking their 2N2222As to a P2N2222A datasheet.

author: Jwillis
author_rank: Super Contributor
timestamp: December 05, 2019, 07:25:28 am
content: The P2N222A and 2N222A are both NPN . The only difference is the PN222A is a plastic case and the 2N222A is a metal case. You have the plastic case . Pin 1 is collector ,2 Base and pin 3 Is the emitter.2N222Ahttps://www.onsemi.com/pub/Collateral/P2N2222A-D.PDFP2N222Ahttps://media.digikey.com/pdf/Data%20Sheets/ST%20Microelectronics%20PDFS/2N2219A,%202N2222A.pdfBesides you take you out put signal from the collector not the emitter.your transistor is backwards

author: mikerj
author_rank: Super Contributor
timestamp: December 05, 2019, 09:03:41 am
content: Quote from: Jwillis on December 05, 2019, 07:25:28 amFor extra confusion, there is also thePN2222Athat uses the more common EBC pinout.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: December 05, 2019, 09:04:25 am
content: Quote from: not1xor1 on December 01, 2019, 06:56:18 amBeing that it was posted in Beginners area of the forum, what did you honestly really expect them to say?

author: austfox
author_rank: Regular Contributor
timestamp: December 05, 2019, 11:04:50 am
content: Quote from: Ed.Kloonk on December 05, 2019, 09:04:25 amMaybe ‘Problem with my common emitter amplifier circuit’.They have a scope so are probably a bit more advanced than a true beginner.