Simpler PI...

[Aziz]

PNP Version

Hi all,

it is really trivial "adapting and arranging"(c)(r)(tm) the NPN version into PNP version. Just flip over some parts. *LOL*
See below:

It should practically work a treat. The spice sim is working a treat.

Well, I could test PNP BJTs later (in March/April).

Cheers,
Aziz

[WM6]

Interested in:

2N3904

BC107, BC108, BC109 (A, B, C version)

[Aziz]

Ok guys,

you have time for further NPN BJT proposals for testing until Sunday.
Aziz

[bernte_one]

simple pi is not ready

does anybody work on complete machine or do all only experiments with single components

why not testing out pi4 from inside the metal detector book in smd version?

[pipolanar]

Hi everyone, i'm from Argentina, i don't speak english well, but i can write some words, (i don't like google translator). I was looking into the circuit "simpler pi..." did someone check the current at mosfet's drain (M2)?

[Aziz]

2N4401
BD139
2SA1316 if you can find it - Rbb~2ohm
2SA1084
ZTX653

Bad luck. Nothing of them found there (except BD139).
2SAxxxx being PNP!
But I'm using NPN currently.
(Although, the schematics can be turned into PNP type as well.)
Aziz

[Aziz]

2N4401
BD139
2SA1316 if you can find it - Rbb~2ohm
2SA1084
ZTX653

Thanks Davor,

I've noted them. I hope to find them at www.reichelt.de
BTW, I had the BD139.
Not bad: 2 x BD139+OP27: en = 0.58 nV/sqrt(Hz)
See below the latest BJT+op-amp AC amplifier version and pure op-amp AC amplifier version noise figures.


I'll make a new comparison with the new parts then.

Cheers,
(¯`*•.¸ /\ziz¸.•*´¯)

[Davor]

2N4401
BD139
2SA1316 if you can find it - Rbb~2ohm
2SA1084
ZTX653

[Aziz]

I have a box full of
BC 549C :: Transistor NPN TO-92 30V 0,1A 0,625W

It won't be different to BC550C. A bad BJT! So much for a so-called "low noise" BJT.

A 2 x BC550C + OP27 at gain=210 achieves 1.8 nV/sqrt(Hz) input referred noise density.
It can't get close to the limits I already have arrived.

Other proposals please.
Cheers,
Aziz

[6666]

I have a box full of
BC 549C :: Transistor NPN TO-92 30V 0,1A 0,625W

[Aziz]

BJTs

Hi all,

has anyone a wish (list) on BJTs I should test them as well?
The BJT must be relative cheap, common and available at www.reichelt.de (where I buy my parts).

We need a collector current rate of 100 mA (better 0.5 A) - 2 A, a relative high hFE and low RB at the same time, which tends to make less noise.
Any proposals?

I'll order the BJTs on Wednesday or Thursday (at least this week).

Cheers,
Aziz

[Aziz]

2 x BC141-16 & OP27 at gain = 210 (measured gain more accurately now, 1k, 4.7 Ohm):
en = 0.48 nV/sqrt(Hz)
So you see, that there isn't much difference to NE5534. Except the OP27 has more output rail and better transfer characteristics (low distortion, low noise, etc..)
Aziz

[Aziz]

Just want to demonstrate, that higher amplifier gain will achieve the goal easily.
en = 0.39 nV/sqrt(Hz) with 2 x BC141-16 and OP27 at gain=434 (measured, 1k and 2.3 Ohm gain setting resistors).
I could even reduce it at much higher gains too (x1000 for instance). But I want to achieve it at low gains (x100 to x200).

Cheers,
Aziz

[Aziz]

Goal Achieved!

Yes!, yes!, yeeeeeeeeeeeeeeeees!
I have achieved my goal of 0.5 nV/sqrt(Hz).
Input referred amplifier noise density for 2 x BC141-16 & NE5534 for gain = 206:
e_n = 0.49 nV/sqrt(Hz)


BTW, I have found in my box two BC141-16. And I have increased the amplifier input referred noise density measurement accuracy. And there are still some transistors to test.

New goal:
0.4 nV/sqrt(Hz)

Cheers,
Aziz

[Davor]

It's raining "blue" pills.

Damn! I took the red one.

Regarding transistor current, if you don't go over ~6mA you are well within op amp supplies. However, once you reach some decent noise levels, the only upside of increasing currents is increasing the preamp frequency response. So in effect a transistor choice is a more determining factor than current.