Ranchu32,
I would think someone could mail you those small transistors fairly easily. What is the postage for a letter size envelope from the US to Aus.?
I would think someone could mail you those small transistors fairly easily. What is the postage for a letter size envelope from the US to Aus.?
It is frustrating that we don't have access to many of the nice small signal stuff, heck even the power transistors, that both mouser and digikey stock.
I don't know what suitable replacement part numbers are for most of these either. I simply bought a reasonable amount of 992/1845 and 3503/its complement, a few years ago just in case.
The nice thing though is that all the amplifiers either use a cascode or regulation for the main input transistors, this keeps the Vce requirements very low. I am positive that farnell stocks at least one type of low noise, high hfe type input transistor, I just don't know what they are. Or at least they will have something better than the 5551.
I don't know what suitable replacement part numbers are for most of these either. I simply bought a reasonable amount of 992/1845 and 3503/its complement, a few years ago just in case.
The nice thing though is that all the amplifiers either use a cascode or regulation for the main input transistors, this keeps the Vce requirements very low. I am positive that farnell stocks at least one type of low noise, high hfe type input transistor, I just don't know what they are. Or at least they will have something better than the 5551.
Something like these perhaps?
2N5088G. - ON SEMICONDUCTOR - TRANSISTOR, NPN, 30V, 0.05A, TO | Farnell UK
2N5088G. - ON SEMICONDUCTOR - TRANSISTOR, NPN, 30V, 0.05A, TO | Farnell UK
That would be wonderful but I don't want to put anyone to the trouble...
If someone were to order say 100 pcs (price break) I'd take 20-30 pcs in an envelope and that way should be assured of a decent matches.
I'm guessing that close matched devices is pretty important for this design and any other symmetrical topology.
The devices are pretty cheap and could be worked into the cost of a set of boards. I buy the KSA992F and KSC1845F a few hundred at a time and it would be easy to send a strip of ten per board. This sound like a possibility?
Matching is a nicety but not a necessity.
Matching is a nicety but not a necessity.
Andrew, thanks a lot for sharing. Very good research.
470 R increased stability of my circuit right away 😉
Cheers,
Valery
Hi Guys,
While I'm waiting for Jason to create some more Gerbers for some of these IPS, I have been thinking of utilizing a pair of Symasym boards that I have. I posted the schematic and OS made some suggestions for resistor changes. I just have a couple more questions. Based on the attached schematic, would I need to change Q1 & Q2 to something other than MPSA18 if I am using +-75V rails? What about Q7 & Q8? Will BC546B be OK? Also, are there any resistors that need to be more than 1/4w and if so, which ones?
Thanks, Terry
While I'm waiting for Jason to create some more Gerbers for some of these IPS, I have been thinking of utilizing a pair of Symasym boards that I have. I posted the schematic and OS made some suggestions for resistor changes. I just have a couple more questions. Based on the attached schematic, would I need to change Q1 & Q2 to something other than MPSA18 if I am using +-75V rails? What about Q7 & Q8? Will BC546B be OK? Also, are there any resistors that need to be more than 1/4w and if so, which ones?
Thanks, Terry
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Terry, you will definitely need to replace the MPSA18 in Q1 and Q2 as these devices see rail voltage + half the input signal at full swing. I think the SA992/SC1845 would be ideal as the 120Vcbo will give you adequate margin.
That one will work but the specs aren't as good as the devices mentioned.
If you insert the SA/SC transistors backwards the pin out will be correct.
If you insert the SA/SC transistors backwards the pin out will be correct.
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Would you remove the input filter (remove C) then measure the bandwidth? I want to know the bandwidth (small signal) of your CFA with 1K/33 feedback resistors.
Actually. KSC is ecb. The MPSA is ebc so the leads would have to be twisted. Maybe possible but not the best solution. The only devices I see that have a base lead in the center and are at least 80V are the MPSA06/42/8099 and the BC546. Not sure if any of these will work.
Thanks, Terry
Hi bimo i have tried this already but i can't see any difference.
I did this test for VSSA (PMI VER.)also. -3db for this VSSA =640KHZ.(10vRMS Out/4R).
If you interesting for bandwidth(small signal)i must repeat all these.
Thimios.
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