matching transistors - DIY

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analogdata
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Post by analogdata » Fri Dec 15, 2017 6:16 am

Apologies if this has been answered a million times.
Chinese transistor tester.
Is this not accurate enough for matching?

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Post by Synthiq » Sat Dec 16, 2017 1:47 pm

analogdata wrote:Apologies if this has been answered a million times.
Chinese transistor tester.
Is this not accurate enough for matching?
The resolution is only 1mV so you can probably get as good result if you just short base and collector together and measure Vbe with your DMM's diode function.

When you measure the difference in Vbe between two transistors as is done in the circuits above, you can use the 200mV range and get 100uV resolution with almost any DMM. The transistors are also measured at the same time so there is also a better chance they have the same temperature than if they are measured sequentially. The Vbe changes 2-2.5mV per degree C so it is critical that the temperature is the same for both transistors to be matched.

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kid303
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Post by kid303 » Sun Feb 18, 2018 10:16 am

Just thought I'd put it out there that I got 3 of the Ian Fritz pcbs modified by Fonitronik and X and Or.

The circuit is the same as Fonitroniks you can see earlier in this thread and has been modified by adding a MOTM header aswell as the 10 pin Eurorack header.

They were only about either $13 or £13, I cant remember posted to the UK from Oshpark.
Thats an incredible service.
You might as well buy some yourself and give them to your friends. I dont know anyone into synth diy so I just tgought I'd offer one to anyone wants one.
Just looked it was $13 which is about £10, I cant believe they can make them for that, I highly recommend their service for prototypes etc.

Right back to the point, If you want one you can have one for £4.00 which is about $5.60 as of today.

Just thought I'd mention it and failing that get 3 for yourself and if you live in the States itll be even cheaper I'm sure.
tHere i the link if you want to get some from Oshpark somewhere in this thred I think, I cant remember but if you type Oshpark and Ian Fritz transistor matcher I'm sure youll find it, I did and I'm fresh off the boat new to this.

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Post by Synth Con Meo » Sun Feb 18, 2018 1:46 pm

kid303 wrote:Just thought I'd put it out there that I got 3 of the Ian Fritz pcbs modified by Fonitronik and X and Or.

The circuit is the same as Fonitroniks you can see earlier in this thread and has been modified by adding a MOTM header aswell as the 10 pin Eurorack header.

They were only about either $13 or £13, I cant remember posted to the UK from Oshpark.
Thats an incredible service.
You might as well buy some yourself and give them to your friends. I dont know anyone into synth diy so I just tgought I'd offer one to anyone wants one.
Just looked it was $13 which is about £10, I cant believe they can make them for that, I highly recommend their service for prototypes etc.

Right back to the point, If you want one you can have one for £4.00 which is about $5.60 as of today.

Just thought I'd mention it and failing that get 3 for yourself and if you live in the States itll be even cheaper I'm sure.
tHere i the link if you want to get some from Oshpark somewhere in this thred I think, I cant remember but if you type Oshpark and Ian Fritz transistor matcher I'm sure youll find it, I did and I'm fresh off the boat new to this.
I was just looking into that PCB on OSHParks site since I just started looking into transistor matching. OSHParks is actually local to me which really doesn't make any difference but I thought it was interesting when I fist found that out. Anyway I was thinking about getting a set from them but quite honestly I really don't know yet how in the hell to use the device.

I've looked at the different websites on using such devices but I get a bit lost into what actually is the procedure to use them. Of course I am pretty new to the whole DIY thing. I have an a ARP 1601 kit that mentions using matched transistors which both are different. One being a NPN and the other a PNP. I know some people mentioned it doesn't matter but I am thinking that it is an excuse for me to learn how to match transistors just in case I really need to on another project.

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Post by kid303 » Sun Feb 18, 2018 2:01 pm

I am new myself and dont knoe how to use it either but from what I can gather from Ian fritzs circuit is you put at least 10v . ino the circuit add two transistors into either the right side which are pnps and left npns and measure the voltage one way for eg the + volt and then flip the switch to - volt and the idea is to measure the voltage difference between them and try to obtain no voltage difference ie the voltage is the same for the two transistors in the + and - voltage.
I think the easiest way is to leave a reference transistor in one socket and measure different ones against that reference one.
I think thats how its done.
As for matching npns to pnps I havent received a decent answer as to how to match them beyond the way you do it for the above.
I guess you would have one npn in the npn side and a pnp in the pnp side and try to match their voltage that way but honestly I'm not clear on that myself.

I only received the pcbs the other day and havent even got any transistors to try the circuit yet.

I still havent been given an answer as to why some people would put these circuits into a Eurorack module.

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Post by emmaker » Sun Feb 18, 2018 4:33 pm

kid303 wrote: As for matching npns to pnps I havent received a decent answer as to how to match them beyond the way you do it for the above.
You have to manually match them separately. Funny thing is that all I've read about this type of expo circuit no one says what parameter they are matched too. So I assume it's gain. Might be wrong though.

This info might be useful.

Electronotes S-019

Electronotes EM37 - Expos

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Ian Fritz's method for matching transistors

Post by cyrdun » Fri Mar 02, 2018 1:17 pm

Hi,
I need to match some pairs of transistors, and Ian Fritz's method seems both accurate and easy to put in place. However, I have two questions concerning his setup :
what should be the value of D1?
I have read that it would work with 15V power, would it work too with 9V power, ie power supplies for guitar pedals?
Thanks in advance! :)

[EDIT] I found this schematic by navigating back in this thread, should do the job :)

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Last edited by cyrdun on Sat Mar 03, 2018 9:12 am, edited 1 time in total.

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Post by APETECHNOLOGY » Fri Mar 02, 2018 1:50 pm

does anyone have a pcb they could sell me?

Kid303?

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gabba@gabi
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Post by gabba@gabi » Sat Mar 03, 2018 11:41 am

there is of course a new kid in town
viewtopic.php?t=153845

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Post by kid303 » Thu Mar 08, 2018 5:36 am

Can anyone tell me if the Ian fritz circuit can be used to measure capacitors as when i look up how to measure a capacitor (for matching purposes) a few articles refer to the use of a wheatstone bridge (which is what Ian Fritz' circuit is, as said by the man himself) which is fed a square or sine wave, but I think a square is better for its on-off properties.
The measurement is then taken with use of an oscilloscope from the 0 to 62.3% and with the aid of an equasion determines the precise measurment of the given capacitor under test, only that is the only way I could find to precisely determine a capacitors value for matching purposes without the use of a curve tracer which evidently I do not posess.

Anyway if someone could tell me if Ian Fritz' circuit could be used, kindly let me know please.
The only difference was that the wheatstone bridge I saw that they used had a capacitor together with the two matched resistors, so I am wondering if Ian's circuit would suffice or whheather that extra capacitor bar the cap. under test is a requirement.

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Post by Synthiq » Fri Mar 09, 2018 6:30 pm

My understanding of the wheatstone bridge is that one component in the bridge is adjusted until the difference between the center point on the left and right side is zero. At that point the impedance ratios between the upper and lower impedance are the same on left and right side and the unknown impedance can be calculated if the other 3 are known. Ian Fritz' circuit isn't really designed to do this so I think it is easier to just get a good multimeter that can measure capacitance and be done with it.

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Post by kid303 » Sat Mar 10, 2018 3:18 am

what is this then, it looks like a wheaystone bridge and on youtube it describes exactly this and I an Fritz' circuit is a wheatstone bridge which he says himself in his article describing his circuit.

Look at this video, if you dont want to watch it all jump to 2.56 where it describes a wheatstone bridge.


Aso this paper
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Post by kid303 » Sat Mar 10, 2018 3:19 am

sorry first time adding a file and couldnt suss it out added it twice by accident.

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Post by cygmu » Sat Mar 10, 2018 9:16 am

Ian says his circuit is "basically just a wheatstone bridge", and indeed there is an overall similarity in the structure of Ian's circuit and the circuit used to match capacitors in that document you attached (and elsewhere, e.g.
http://www.play-hookey.com/ac_theory/ra ... _apps.html )
but they are not identical. For one thing, the transistor matching setup is DC powered while you need an AC arrangement for capacitors.

If you had a bare PCB for Ian's transistor circuit, you could almost certainly hack it up so that it gave you the cap matching circuit instead -- but the cap matching circuit is so simple in the first place, you might as well just build it.

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Post by kid303 » Sat Mar 10, 2018 9:18 am

the important thing is the square wave being fed into it from a function/signal generator

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Post by kid303 » Sat Mar 10, 2018 9:19 am

meant to say the square wave is important

Is that right

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Post by cygmu » Sat Mar 10, 2018 9:32 am

I think the document you attached described using a high frequency sine wave. But yes, the important thing is that it is a wave that has an AC component so that the frequency-dependent impedance of the capacitors has an effect.

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Post by kid303 » Sat Mar 10, 2018 10:09 am

I think a square is better for the clear on off component rather than the gradual sine wave.

Bloody hell why are some things not striaght forward I just want to match some caps to within 1%

Trouble is I'm really really bad at maths and I dont know how to ascertain what 1% of 1.5 is

Basically Yusynth has four 1.5nF caps matched to 1% but I dont know how much deviation this allows either side
I worked out that 1% of 1.5 is 1.5 divided by 0.01 which is 0.015 but how would that read on a multimeter.

Sorry this is primary school stuff but I was just a class joker and never paid attention, I found out a few years ago that I'm dyslexic which explains a lot.

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Post by cygmu » Sat Mar 10, 2018 12:43 pm

If your meter is like mine you will get readings like 1.503 or 1.494 etc. You want all four caps to have values within 0.015 of each other. So 1.494 and 1.053 are ok (0.009 apart) buy 1.494 and 1.510 would not be (0.016 apart).

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Post by Synthiq » Sat Mar 10, 2018 2:08 pm

kid303 wrote:Look at this video, if you dont want to watch it all jump to 2.56 where it describes a wheatstone bridge.
Actually, this is not a wheatstone bridge. If you measure the output with an oscilloscope, the probe capacitance and to some degree the probe resistance will unbalance the circuit and must be compensated for to get an accurate result. If you don't care about absolute accuracy and only want to match two capacitors the circuit may work but will still require some math to convert the difference in under- or overshoot to a mismatch error.

The pdf file may describe a bridge circuit but it is really used as two independent RC networks driven by the same ac signal. If I used this circuit I would swap the resistors and capacitors so they would act like lowpass filters and I would measure the difference in rise/fall times when driven by a square wave as you suggested. Assuming you have matched the resistors to much better than 1%, the oscilloscope channels gains are match to much better than 1% and you have better eyesight than I do you may be able to match the capacitors to 1% by measuring the difference in rise time for the two channels.

But still, I have a cheap digital multimeter that can measure a 1.5nF capacitor with 1pF, or 0.07%, resolution in a second or two so why make life so complicated for yourself? If you have access to an oscilloscope, you sure have access to a decent multimeter, right?

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Is my multimeter resolution enough?

Post by cyrdun » Sat Mar 17, 2018 10:16 am

Hi,
I'd like to know if my multimeter resolution is enough for matching transistors? From the manual it seems to be 3 3/4, but I don't really get what it means, especially the fraction.
My aim is to match transistors for the Guinguin Model D clone, discussed in other threads on this forum.
Thanks in advance! :)
Image[/img]

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Post by Synthiq » Sat Mar 17, 2018 11:16 am

The most common multimeter resolution is 3 1/2 digits which translates to a maximum count of 2000 (or 1999 to be precise). 3 3/4 has a higher maximum count and is used to describe multimeters with a maximum count of 4000 as in this case but also for a maximum count of 6000.

If you use it to measure voltage difference between two transistor emitters as in Ian Fritz' circuit you use the 400mV range and have a 0.1mV resolution which is enough for you. If you measure the voltage between base and emitter on a single transistor (like a diode test) you need to use the 4V range and only get 1mV resolution, which I would consider marginal but depends on the matching requirements.

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Post by cyrdun » Sat Mar 17, 2018 11:38 am

Synthiq wrote:If you use it to measure voltage difference between two transistor emitters as in Ian Fritz' circuit you use the 400mV range and have a 0.1mV resolution which is enough for you. If you measure the voltage between base and emitter on a single transistor (like a diode test) you need to use the 4V range and only get 1mV resolution, which I would consider marginal but depends on the matching requirements.
Hi, I'm using this version : schem

I've tested 6 transistors so far, it always gives me 0mV, I find it too beautiful to be true?

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Post by Synthiq » Sat Mar 17, 2018 1:28 pm

That sounds too good to be true. Measure the collector-emitter voltage of both transistors to make sure they are correctly biased at 0.6-0.7V. Also make sure the supply voltage to the circuit is there. Otherwise no current is flowing and you would always read 0mV.

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Post by cyrdun » Sat Mar 17, 2018 2:02 pm

Synthiq wrote:That sounds too good to be true. Measure the collector-emitter voltage of both transistors to make sure they are correctly biased at 0.6-0.7V. Also make sure the supply voltage to the circuit is there. Otherwise no current is flowing and you would always read 0mV.
Thank you :). I think I have to double-check my circuit, I've made it on a stripboard so it is open to errors, at least for me.
What is weird is that my multimeter gives me changing random values when in DC mode and not connected to anything? Shouldn't it be 0mV too?

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