the Tail of a Long Tail (transistors)

[Analog_Fan]

if the input is 10V the output is 10V.p.p.
At 6V the output is 8V.p.p
At 4V the output is 5V.p.p. (in the Falstad Simulator, to get an idea on what resistors i have to have at hand, i did build the Circuit as well in LTSPICE).
At 2V = close to 1.6V.p.p.
the VCA starts moving at a control voltage of 1.5V.

That's makes it logarithmic or exponential?

Using the beta calculator of Paul for MOSFETS.
https://www.falstad.com/circuit/mosfet-beta.html

RDS(on) (Ω) (use typical value):
VGS where measured (V):
Threshold (V) (use typical value):

don't know what to fill in, what is RDS(on).

default = 20m.

the gates are at 2.5V, halfway using voltage dividers.

What number am i looking for the ALD1105?

 

[user 37518]

That is just a current mirror. You have to specify to us which is what you call the output and which is the input. Depending on the voltage you apply at the Scaled_CV_B input, you will get a current at the collector of transistor B of roughly IC = (Voltage-0.7)/8.2K

RDS on is the resistance between drain and source of an FET when it is fully turned on, it is a very important parameter when the FET will be used in switching applications such as switch-mode PSUs. You can look it up in the transistor data sheet, or better yet, you can use a good simulator and download the SPICE model for the specific FET you want to use rather than just guessing.

The datasheet for the ALD1105 says that RDSon is 350-500 ohm for the N channel, and 1200-1800 ohm for the P-Channel. Again, you need a good SPICE model, just using that 3 parameter calculator won't do you much good. Seriously, the faster you switch to a good simulator with good SPICE models, the more you will progress. The simple FET quadratic formula which is used by the Falstad calculator, is an extreme oversimplification of an FET, SPICE models take into account much more parameters and they are more accurate.

 

[Analog_Fan]

That is just a current mirror. You have to specify to us which is what you call the output and which is the input. Depending on the voltage you apply at the Scaled_CV_B input, you will get a current at the collector of transistor B of roughly IC = (Voltage-0.7)/8.2K

yeah and thank you,

i know that this is not the long pair, but the lower part off it.
But it seams to move exponential, it amplifies (the upper part) a lot at small control voltage but seems to slow down above 6/7 volt.

i tried adjusting resistor values to have full amplification at 10V and 50% of that at 5V, but whatever i did, it wasn't possible. i did spend hours on it.
But a VCA is supposed to be exponential, i remembered.


Project 213
Q3/Q4 ... accept the capacitors witch seems to be bad.

IC = (Voltage-0.7)/8.2K

didn't know that

 

[user 37518]

yeah and thank you,

i know that this is not the long pair, but the lower part off it.
But it seams to move exponential, it amplifies (the upper part) a lot at small control voltage but seems to slow down above 6/7 volt.

i tried adjusting resistor values to have full amplification at 10V and 50% of that at 5V, but whatever i did, it wasn't possible. i did spend hours on it.
But a VCA is supposed to be exponential, i remembered.

View attachment 93917
Q3/Q4 ... accept the capacitors witch seems to be bad.

You said you spent hours in it, are you just messing around?

The upper part is a current out to a trans-impedance amplifier (U1) which converts the current to voltage, resistors R10 and R11 determine the transimpedance gain.

Exactly what seems to be bad about the capacitors? looks to me that you are just using the Falstad sim and messing around with the values, and taking decisions based on wild guesses. That is ok to learn, but really, you should try to study the circuit, rather than just say that the capacitors are bad for no apparent reason or justification.

My 2 cents

 

[Analog_Fan]

but really, you should try to study the circuit, rather than just say that the capacitors are bad for no apparent reason or justification.

that's the idea.

tomorrow, I'll be receiving a real physical recommended book by Robert Pease.

Math aint the problem, know the formula's, i know what the HFE is, but that's about it, more or less.
the npn is easy, but the pnp? no matter how many video's i have seen about transistors and they mostly talk about the npn.
put 1mA at the base and it will pull along 100mA, if i'm correct.

i'm not saying the capacitor is bad, but it has a effect, slowly rising.

 

[user 37518]

that's the idea.

tomorrow, I'll be receiving a real physical recommended book by Robert Pease.

Math aint the problem, know the formula's, i know what the HFE is, but that's about it, more or less.
the npn is easy, but the pnp? no matter how many video's i have seen about transistors and they mostly talk about the npn.
put 1mA at the base and it will pull along 100mA, if i'm correct.

i'm not saying the capacitor is bad, but it has a effect, slowly rising.

PNP is the same as NPN, current just flows the opposite way, that's basically what you have to know. If you want to go deeper, you can learn that in the PNP the holes are the majority carriers, etc.. but the bottom line is if you understand the NPN , PNP is just the other way around. There is more minutae between them, but get the basics right first.

Just as a suggestion, the book by Bob Pease will probably be too advanced for you and it wont cover the basics, which is what you have to know. Look in the Analog Books recommendations, I made a post with many book recommendations, you need to start with an Electronic Devices book and a Circuit Analysis book, don't try to run before walking.

 

[Analog_Fan]

PNP is the same as NPN, current just flows the opposite way, that's basically what you have to know. If you want to go deeper, you can learn that in the PNP the holes are the majority carriers, etc.. but the bottom line is if you understand the NPN , PNP is just the other way around. There is more minutae between them, but get the basics right first.

Just as a suggestion, the book by Bob Pease will probably be too advanced for you and it wont cover the basics, which is what you have to know. Look in the Analog Books recommendations, I made a post with many book recommendations, you need to start with an Electronic Devices book and a Circuit Analysis book, don't try to run before walking.

the Basics i had at school, that's what i did back then, e.e., but i haven't spend using it the other 50% of my life with electronics.
i worked on boats, cars, jet skies, Yachts, i have built the national optical fiber network, as simple electrician for houses and companies and others things. fixed people computers.
I also spends tons of hours on programming. nad have a pretty high ranking vs people on Universities.

I have build quite a lot of Synthesizer modules, the pcb's i make are pieces of technical art.
i used Sources, Like Moog, Buchla, Korg ... and where i could i improved on it.
It's works great, but this experiment is different.

i'm aware of the holes, carriers and depletion zone, but not the corresponding math.

I have set myself a new goal, make sure it uses as little as possible current.
: )

 

[user 37518]

the Basics i had at school, that's what i did back then, e.e., but i haven't spend using it the other 50% of my life with electronics.
i worked on boats, cars, jetskies, Yachts, i have built the national optical fiber network, as simple electrifcian for houses and companies and others things.
I also spends tons of hours on programming. nad have a pretty high ranking vs people on Universities.

I have build quite alot of Synthesizer modules, the pcb's i make are pieces of technical art.
i used Sources, Like Moog, Buchla, Korg ... and where i could i improved on it.
It's works great, but this experiment is different.

i'm aware of the holes, carriers and depletion zone, but not the corresponding math.

ok, it was just a suggestion, seems to me that you don't have the basic concepts very clear, knowing how a PNP transistor works, is electronics 101, but it seems like you prefer the hands on approach. The best of luck

 

[Analog_Fan]

ok, it was just a suggestion, seems to me that you don't have the basic concepts very clear, knowing what a PNP transistor is, is electronics 101, but it seems like you prefer the hands on approach. The best of luck

desoldering stuff is a pain.

the long tails seems a miracle, move one leg to make another move.
did you ever check on the Bucha 259?

normally i use lm13700 or CA3080.

 

[ccaudle]

based on wild guesses. That is ok to learn

That is a little bit like how electronic devices were first characterized (in early years of the 20th century). It took many years. I much prefer reading books that distill the knowledge it took the early pioneers years and decades to understand into a nice summary based on modern understanding of how the devices work.

 

[user 37518]

That is a little bit like how electronic devices were first characterized (in early years of the 20th century). It took many years. I much prefer reading books that distill the knowledge it took the early pioneers years and decades to understand into a nice summary based on modern understanding of how the devices work.

Yeah, that's how Lee De Forest basically invented the triode without ever really understanding how it worked, but since then, a lot of theory has been created, network synthesis, semiconductor theory, quantum theory, etc.... since Steinmetz introduced phasors, and basically electric circuit analysis as we know it, things haven't been the same. Actually, Steinmetz complained that engineers knew zero math back in his day, and he was a great influence on the modern curricula for engineering schools as we know it today, by being heavily based on physics and math. Back then it was basically trial and error, did the motor burn? bring in a bigger motor and try again....

Like I said, there is a place for messing around with a simulator, but you should really try to know and understand what you are doing, besides, these circuits are like 50 years old, there is no longer need for characterization, just read the literature, understand how they work, and then mess around but with a purpose, not just fumble the values and see what the simulator outputs. I don't know, that is not my style, I've always been more of an armchair engineer rather than a bench engineer, I don't feel comfortable if I don't know the analytical aspect of a circuit and the math behind it, I feel like I don't understand the circuit if I can't calculate all the currents, transfer functions, etc... But some of the great ones, like Jim Williams, made circuits based on how monkeys in a zoo played around, so I reckon that there are great engineers out there who don't know "the math" perfectly and do amazing things, but then again, not everyone is like Jim Williams...

 

[Analog_Fan]

... as we know it today, by being heavily based on physics and math.

i guess we're losing that, they now provide school kids with(free) ocular / meta inc. virtual reality "glasses" to play in Meta.
Atleast some school here use these, they are putting big money in this virtual world thing.

Like I said, there is a place for messing around with a simulator, but you should really try to know and understand what you are doing, besides, these circuits are at least 40 years old, there is no longer need for characterization, just read the literature, understand how they work, and then mess around but with a purpose, not just fumble the values and see what the simulator outputs. I don't know, that is not my style, I've always been more of an armchair engineer rather than a bench engineer, I don't feel comfortable if I don't know the analytical aspect of a circuit and the math behind it, I feel like I don't understand the circuit if I can't calculate all the currents, transfer functions, etc... But some of the great ones, like Jim Williams, made circuits based on how monkeys in a zoo played around, so I reckon that there are great engineers out there who don't know "the math" perfectly and do amazing things, but then again, not everyone is like Jim Williams...

triode, I saw some black and white video on Tube, made in the or around 60ties?
Thomas Edison also had a part in this. He discovered that the filament of his light bulb always failed at the positive pole .. and he was playing with a grid or something like that to prevent that, he was right about the electrons, but failed the understanding how.

Yeah, i know the long tail is old and i could just copy one from the many examples out there, Like Farm VCA, but I'm giving it some thought, because i adding some features and the max width constraint is just 19mm x 110mm.
I started 6 months ago with the circuit , i have literally thousands of transistors bought in bulk, 500 pcs per bag, Just recently i added new resistor to my list and i still fail some values.
but i do lack a accurate multi meter, mine is off by like 25/30% if i measure a 4k99, i get 3Kxx
a Fluke will set you back 350€

 

[Newmarket]

but i do lack a accurate multi meter, mine is off by like 25/30% if i measure a 4k99, i get 3Kxx
a Fluke will set you back 350€

Apart from anything else - if you get a result this far off then either your meter is faulty or there's something dodgy with a test lead - always worth checking. I recently got odd but believable results with an oscilloscope and eventually it turned out to be the lead.
Get a new multimeter. I don't know why you mention a 350 Euro Fluke. I can buy something to do the resistance sorting work and a lot more for well under £15. And if I decided it had to be a Fluke then prices start at under £150.

 

[Analog_Fan]

Apart from anything else - if you get a result this far off then either your meter is faulty or there's something dodgy with a test lead - always worth checking. I recently got odd but believable results with an oscilloscope and eventually it turned out to be the lead.
Get a new multimeter. I don't know why you mention a 350 Euro Fluke. I can buy something to do the resistance sorting work and a lot more for well under £15. And if I decided it had to be a Fluke then prices start at under £150.

mine was 25€ years ago.
good enough to do most things, accept precision.
that price came fro the local mayor electrics parts supplier where electricians and so buy there stuff.
You have to pay extra for the leads with alligator clips, i think it's 25€ per lead and why its sums to 350€

But maybe i could check if the leads are bad.

 

[JohnRoberts]

But some of the great ones, like Jim Williams, made circuits based on how monkeys in a zoo played around, so I reckon that there are great engineers out there who don't know "the math" perfectly and do amazing things, but then again, not everyone is like Jim Williams...

RIP.... that Jim Williams was willing to paint outside the lines. I recall communicating with him about one of his published circuits. He played with using CMOS logic gate inverters as linear gain stages with NF. He didn't warn readers about the potential current draw and power dissipation from using gates as linear stages with both output devices active at the same time while using too much PS voltage. Effectively trying to pull up and down at the same time. No beuno.

JR

 

[Analog_Fan]

Jim Williams

good that you remind me, i have to walk to the bookshop.

 

[ccaudle]

like Jim Williams, made circuits based on how monkeys in a zoo played around

I think that is a mischaracterization of how Jim Williams worked. If you read his writings you can see he had a deep understanding of how electronic devices work. He was playful, but he wasn't playing around.

 

[ccaudle]

if you get a result this far off then either your meter is faulty or there's something dodgy with a test lead

Or you are holding the leads to the device with your fingers and are measuring the parallel resistance of the device and your body.

You have to pay extra for the leads with alligator clips

 

[Analog_Fan]

if you design semiconductors ...

check out this interesting video from Fran, made in the 60ties.


it takes a whole lot of math, apparently.

 

[Newmarket]

Or you are holding the leads to the device with your fingers and are measuring the parallel resistance of the device and your body.

yeah - I guess we've all done that at some point.
But it doesn't 'turn' 5K0 into 3K0 - unless you are very conductive for a human being