Discrete Opamp Open Design

[keantoken]

Yeah, I was a bit too hasty posting those models. These ones have a smidge of flicker noise modeled and have the right Rb values.

.model BC337-40_kq NPN(
* Updated Rb 8-20-2014 by keantoken
+ IS=7.809E-14 Ibc=100f NF=0.9916 ISE=15f NE=1.4 Nk=0.55
+ BF=436.8 IKF=1.15 VAF=103.6 NR=0.991 ISC=6.66E-14 NC=1.2
+ BR=44.14 IKR=0.09 VAR=14 Rb=17.4 Kf=30f IRB=2.00E-04 RBM=8
+ RE=0.12 RC=0.05 Rco=3 XTB=0 EG=1.11 XTI=3 CJE=80p
+ VJE=0.6657 MJE=0.3596 TF=620p XTF=1.5 VTF=2 ITF=0.5 PTF=88
+ CJC=1.306E-11 VJC=0.3647 MJC=0.3658 XCJC=0.455 TR=2.50E-08
+ CJS=0 VJS=0.75 MJS=0.333 FC=0.843 Vo=500 Gamma=4n Qco=8n
+ Vceo=45 Icrating=800m mfg=OnSemi)
.model BC327-40_kq PNP(
* Updated Rb 8-20-2014 by keantoken
+ IS=2.077E-13 Ibc=230f NF=1.005 ISE=1.4f NE=1.3 NK=0.5
+ BF=475 IKF=.65 VAF=29 NR=1.002 ISC=2.963E-13 NC=1.25
+ BR=20.92 IKR=0.104 VAR=10 RB=17.4 Kf=240F IRB=1.00E-05
+ RBM=5.3 RE=0.14 RC=0.32 Rco=3.75 XTB=0 EG=1.11 XTI=3
+ CJE=115p VJE=0.9296 MJE=0.456 TF=500p XTF=3.25 VTF=2.5
+ ITF=0.79 PTF=80 CJC=2.675E-11 VJC=0.8956 MJC=0.4638
+ XCJC=0.459 TR=3.50E-08 CJS=0 VJS=0.75 MJS=0.333 FC=0.935
+ Vo=500 Gamma=10n Qco=8n Vceo=45 Icrating=800m mfg=OnSemi)

 

[31697B]

John -- What are the P/N for a complimentary pair of transistors which have Rbb = 2-4 Ohms, high voltage and high beta? And, still available.
I would like to test them for linearity.


THx-RNMarsh

 

[Joachim Gerhard]

Zetey and NXP make so called BISS transistors.
They have super low Rbb`and some have high Hfe.
They do not have high voltage though.
Why not do a workaround ? Those Japanese " super " transistors where just an internal Faulkner circuit on a dye.
Say two BC327-40 and BC337-40 in a parallel symmetric circuit ?
I got the folowing numbers ( except 1/f at very low frequencies ) :
Run each transistor on 3mA collector current.
That makes 6mA in a row, push pull so 12mA.
1/ 0.12mS = 8.333 devided by 4 = 2.083 plus Rbb`( 3.332 ) = 5.415 Ohm voltage noise.
That is as good as it gets.
You could even crank up the collector current to say 10mA each but then the early voltage of the PNP goes astray and you end up with more distortion.
Not that this matters much for an MC input.
Say your MC cart pulles out .5mV with 5cm/ sec. The maximum that can be cut is 100cm/ sec but only over 10kHz than we have a maximum input of 0.5 x 20 = 10mV.
Even take into account ticks and pops this is vitually nothing.
For your use in a line stage ( you do not use vinyl, do you ? ) it makes no sense to design for ultra low voltage noise anyway because with BJs there is always a tadeoff between voltage and current noise.
For distortion cancelation ala Keantoken it may be important to have ultra low Rbb´
though because they conform better to an exponential law.
That can be compensated for though.
Do you guys really know what you want ?
I am not sure or you are hiding your " secrets ".
" This world is an open secret " Buddha.

 

[31697B]

Zetey and NXP make so called BISS transistors.
They have super low Rbb`and some have high Hfe.
They do not have high voltage though.

For your use in a line stage ( you do not use vinyl, do you ? ) it makes no sense to design for ultra low voltage noise anyway because with BJs there is always a tradeoff between voltage and current noise.
For distortion cancellation ala Keantoken it may be important to have ultra low Rbb´ though because they conform better to an exponential law.
That can be compensated for though.
Do you guys really know what you want ?
I am not sure or you are hiding your " secrets ".
" This world is an open secret " Buddha.

..... true, I do not listen to LP's. Its line levels all the way thru.

Myself, I am more interested in power amps of 200-300W size..... much harder... larger Volts and Amps, etc. BUt this place here is line level amps only. Not MM or MC.


THx-RNMarsh

 

[1audio]

The VBIC model in LTSpice has a third noise parameter that may help modeling noise, but the first time I tried to use the model I got a buggy operating point, so I'm waiting to see what the LTSpice coder has to say about it.

Richards measurements suggest a 1/f corner near 1 KHz. That's pretty high for a low noise device. I have seen some interesting low noise parts that have noise corners in the 100 KHz range once you look at the whole datasheet. Its a shame because what could be better marketing than using GASfets. (Imagine the possibilities for slogans and slurs.)

 

[Joachim Gerhard]

Then BC550, 560 are fine ( on rather low idle, watch the early voltage in PNP ) or the usual Japanese substitudes.
Fairchild makes more or less the same, they are not called SC, SA but KSC, KSA.
My Prof. Malkolm Hawksford liked the BC550/560 better in a Faulkner arrangement then the (in ) famous super low Rbb`ROhms of the day.
Thanks anyway to measure the voltage noise of the BC327/ 337.
They came out better then i thought.

 

[31697B]

..... I do not listen to LP's. Its line levels all the way thru.

Myself, I am more interested in power amps of 200-300W size..... much harder... larger Volts and Amps, etc. BUt this place here is line level amps only. Not MM or MC.


THx-RNMarsh

See #8 and #9 from beginning to find out what this is (was) about.
....measuring noise is just a pleasant deviation....

-RM

 

[Joachim Gerhard]

GASFets have very high 1/F.
I just talked to Burkhard Vogel.
In the next issue of Linear Audio you will see about 1/F. We have a quarell, but
Gentlemen, BUY THAT ISSUE.

 

[Joachim Gerhard]

I hate noise and i hate to measure it so we are gemini.

 

[Joachim Gerhard]

Nothing beats the Sanyo video transistors for power amps.

 

[Joachim Gerhard]

I mean in the VAS.
Who coined that name ?
I find it awkward.
That is not the only stage in a typical power amp that does voltage amplification.

 

[31697B]

Hi Demian, Joaachim,

I have looked at some microwave devices when I worked at LLNL. Some are designed to be run class A with high current/bias. They also must be linear in single-ended operation in many cases. Low IM is important for RF and so many microwave amplifier devices are quite linear.

THx-RNMarsh

 

[Joachim Gerhard]

Yes, GasFets excell at RF.
I worked in a microwave lab too, so what ?

 

[Joachim Gerhard]

Tubes have it all if it where not because of their mechanical deficiencies.

 

[kgrlee]

Zetey and NXP make so called BISS transistors.
They have super low Rbb`and some have high Hfe.
They do not have high voltage though.
Why not do a workaround ? Those Japanese " super " transistors where just an internal Faulkner circuit on a dye.

Can you do a sketch of the 'Faulkner circuit?

And what are the Zetex and NXP items that have super low rbb'?

If they are readily available, Mr. Marsh can test them. The rest of us can look at datasheets & drool.

Some of us still have practical applications for very low voltage noise.

With the right devices, it is possible to get within 1dB of http://www.hoffmann-hochfrequenz.de/downloads/lono.pdf with very simple circuits for a 5R source.

What do you use Iono for?

 

[Joachim Gerhard]

Faulkner is an english EE professor. He found that paralleling higher voltage noise BJT´s lowered the noise by the square root. That was in the 60s.
The Japanese captured up and put many smaller BJTs on one die comming up with the low Rbb`types.

 

[Joachim Gerhard]

JC was the first that took advantage of this information and got a pattent.
That was the Levinson Pre-Pre in it´s various disguises.
IET Digital Library: The design of low-noise audio-frequency amplifiers

 

[Joachim Gerhard]

The Douglas Self is an example.
The Lee is the parallel symmetric idea i proposed.
There 4 transistors are in parallel because of the push-pull action.
You could say that you have to watch the base-emitter resistance to ground.
Any resistor in the base ( base stopper ) or from emitter to ground ( degeneration adds to the voltage noise comprising out of Johnson noise plus excess noise the resistor may have).
It´s a tricky business but it can be managed.

 

[Joachim Gerhard]

You can go to the Salas Simplistic thread.
There are a lot of axamples of paralleling for lower noise for example the Naim.
It work somehow with J-fets too.
The have a higher 1/F though.
Fletcher-Munson helps here plus the noise from a J-fet is somewhat more " benign " in character because it does not have " popcorn nose " like some BJT can.
it´s an annoying impulsive type that draws the attention away from the music.
Cleaner modern processes do not have that problem

 

[Joachim Gerhard]

http://www.angelfire.com/sd/paulkemble/sound4.html
Here is the D.Self and the Lee.