> No PNP complementary.
Not a problem for me, since the circuit is a Lin-Bailey with 2 x 2sa992 PNP LTP with resistive collector load driving the NPN VAS with bootstrapped collector load.
For complementary drivers/predrivers, I'm happy with the 2sd669/2sb649 - I don't need the 400 MHz fT for an EF.
>Easier to order original A1538/C3953 from the Lab in Georgia.
I get the Fairchild NPN clones off-the-shelf, retail, locally in India, since it's apparently widely used in CRT monitors as the video driver/cascode. Commodity pricing, too.
But you're right - I need to find a complementary pair for experimenting with topologies like the Symasym, FC100, etc. For the moment, I'm stuck with the d669/b649.
Not a problem for me, since the circuit is a Lin-Bailey with 2 x 2sa992 PNP LTP with resistive collector load driving the NPN VAS with bootstrapped collector load.
For complementary drivers/predrivers, I'm happy with the 2sd669/2sb649 - I don't need the 400 MHz fT for an EF.
>Easier to order original A1538/C3953 from the Lab in Georgia.
I get the Fairchild NPN clones off-the-shelf, retail, locally in India, since it's apparently widely used in CRT monitors as the video driver/cascode. Commodity pricing, too.
But you're right - I need to find a complementary pair for experimenting with topologies like the Symasym, FC100, etc. For the moment, I'm stuck with the d669/b649.
I got me a bunch of A1538/C3953 from Evita in Vilnius(Lithuania), for ~$0.45/pc.
The fun part : they're a Nedis contractor, if i order the same parts from the Nedis store overhere the cost is a multitude of what i paid long distance.
The fun part : they're a Nedis contractor, if i order the same parts from the Nedis store overhere the cost is a multitude of what i paid long distance.
Andrew,
I really have no idea!!
Whatever they use on their test rig for the device specs!!
Gadzooks man, you're asking me? I know nothing about these devices, just like the sound they make........
Hugh
I really have no idea!!
Whatever they use on their test rig for the device specs!!
Gadzooks man, you're asking me? I know nothing about these devices, just like the sound they make........
Hugh
Manufacturers generally use either 10Vce or 30Vce but your <2pF @ 30Vce is lower than the majority of good candidates for VAS duty.
Andrew,
1.8pF is quoted for the C3423 at 30V Vce, @ 1MHz.
This device has been my preferred VAS for some years......
Hugh
1.8pF is quoted for the C3423 at 30V Vce, @ 1MHz.
This device has been my preferred VAS for some years......
Hugh
syn08 said:
Excellent syn08. Looks like a top performer for cheap. Is it possible to get F grade hfe parts only?
AKSA said:
Agreed.
My usual source is WES components.
Anyone know a cheaper source of these devices.
cheers
Terry
Hello
I've found some very interesting output, I will try those soon or later, they may go good with the KSC3503/KSA1381
NJL3281 and NJL1302 ThermalTrak Transistor
http://www.onsemi.com/PowerSolutions/product.do?id=NJL3281D
http://www.onsemi.com/pub/Collateral/AND8196-D.PDF
Bye
Gaetan
I've found some very interesting output, I will try those soon or later, they may go good with the KSC3503/KSA1381
NJL3281 and NJL1302 ThermalTrak Transistor
http://www.onsemi.com/PowerSolutions/product.do?id=NJL3281D
http://www.onsemi.com/pub/Collateral/AND8196-D.PDF
Bye
Gaetan
Hugh,
Dont sell the 2SC3423 too short, technically 1.5pf at 30v VCE 🙂, 1.8pf at 10V and higher than 30v even lower, but by .1pf or so, provided every specimen follows the datasheet specs
. This bjt was a revelation to me when I tried it in a previous amplifier as per Hughs suggestion, the 2SC2705 has identical specs but lower dissipation.
Best Wishes
Colin
Dont sell the 2SC3423 too short, technically 1.5pf at 30v VCE 🙂, 1.8pf at 10V and higher than 30v even lower, but by .1pf or so, provided every specimen follows the datasheet specs
. This bjt was a revelation to me when I tried it in a previous amplifier as per Hughs suggestion, the 2SC2705 has identical specs but lower dissipation.Best Wishes
Colin
Hi Colin,
You are right - an exceptional device, but difficult to source in Oz. I like 2SA1360, too. Very nice device but I admit to needing something with a bit more Vceo, say 160V.
Terry,
I buy 1K+ from Peacock Industrial in Singapore, around 35c US.
Cheers,
Hugh
You are right - an exceptional device, but difficult to source in Oz. I like 2SA1360, too. Very nice device but I admit to needing something with a bit more Vceo, say 160V.
Terry,
I buy 1K+ from Peacock Industrial in Singapore, around 35c US.
Cheers,
Hugh
The 2sc3953 is more linear than the 2sc3423, with smaller dependence of Ic on Vce out to about 100 mA Ic on the c3953. Hfe vs. Ic is dead flat out to 100 mA on the c3953, but starts dropping off at ~10-20mA on the c3423 - but it's probably twice as high on average for the c3423. fT peaks at ~400MHz/5 mA for the c3953 vs. ~250MHz/20 mA for the c3423. Slightly higher Cob at 2 pF for the c3953 at 30V, vs. ~1.5pF for the c3423. SOA also looks nice for the c3953 at 70v/100mA, while SOA for c3423 is not spec'ed on the datasheet I have.
Would I trade the linearity/fT/SOA of the c3953 for the lower Cob/higher hfe on the c3423? Probably not - I'm using Cdom >50 pF, so 0.5pF isn't important. Hfe isn't that important if cascoded, and I can also recover some of it in a common-emitter VAS by simply using hi-beta PNPs in my LTP. Above all, I'm paying only about $0.20 each for the c3953 at local retail - the price isn't important, but consistent availability is. The c3423 is often unobtainium, locally - and Toshiba is a prime target for counterfeiters at any rate. OTOH, nobody is going to bother counterfeiting a 20c commodity video driver like the c3953.
Sanyo 2sc3504 also looks interesting with Cob ~ 1.5 pF, but its sweet area of operation extends only to Ic = 3-5 mA. It's also less rugged in a TO-92 package.
Edit: Hugh, nobody here stocks the Fairchild c3953 in 1000+ qty, or I'd be able to handily beat your 35c price on the c3423 *and* make a tidy profit 🙂
Would I trade the linearity/fT/SOA of the c3953 for the lower Cob/higher hfe on the c3423? Probably not - I'm using Cdom >50 pF, so 0.5pF isn't important. Hfe isn't that important if cascoded, and I can also recover some of it in a common-emitter VAS by simply using hi-beta PNPs in my LTP. Above all, I'm paying only about $0.20 each for the c3953 at local retail - the price isn't important, but consistent availability is. The c3423 is often unobtainium, locally - and Toshiba is a prime target for counterfeiters at any rate. OTOH, nobody is going to bother counterfeiting a 20c commodity video driver like the c3953.
Sanyo 2sc3504 also looks interesting with Cob ~ 1.5 pF, but its sweet area of operation extends only to Ic = 3-5 mA. It's also less rugged in a TO-92 package.
Edit: Hugh, nobody here stocks the Fairchild c3953 in 1000+ qty, or I'd be able to handily beat your 35c price on the c3423 *and* make a tidy profit 🙂
Thank you very much LXG,
I appreciate this very good advice, and will look into it.
Damn, just discovered it's only Vceo of 120V. Hmmm.....
I need some 1360s, so will seek out the complement of C3953. (A1358?)
Fascinating...... ain't the net grand??
Hugh
I appreciate this very good advice, and will look into it.
Damn, just discovered it's only Vceo of 120V. Hmmm.....
I need some 1360s, so will seek out the complement of C3953. (A1358?)
Fascinating...... ain't the net grand??
Hugh
Hello Hugh,
Why not drive the VAS in Common Base fashion[folded cascode, Rush cascode CC-CB etc types but not CE-CB] and get rid of majority of artefacts arisen due to Cob.....
regards,
Kanwar
Why not drive the VAS in Common Base fashion[folded cascode, Rush cascode CC-CB etc types but not CE-CB] and get rid of majority of artefacts arisen due to Cob.....
regards,
Kanwar
Yes, Kanwar,
Can be done, and Roender has done it......
I like grounded base drive too, very good HF, but this in truth works against you in an AF amp, and the drive must be presented by folded cascode, with consequent issues for OLG if used in SE, my preferred option.
2SC3600/2SA1406 is looking good; these are Vceo of 200V, Ic of 100mA, Pd of 1.2W, ft of 400MHz, and Cob of just 1.4pF with medium beta available in four grades to 320.
Old device, too, wonder if they are readily available.....
Hugh
Can be done, and Roender has done it......
I like grounded base drive too, very good HF, but this in truth works against you in an AF amp, and the drive must be presented by folded cascode, with consequent issues for OLG if used in SE, my preferred option.
2SC3600/2SA1406 is looking good; these are Vceo of 200V, Ic of 100mA, Pd of 1.2W, ft of 400MHz, and Cob of just 1.4pF with medium beta available in four grades to 320.
Old device, too, wonder if they are readily available.....
Hugh
>2SC3600/2SA1406 is looking good; these are Vceo of 200V, Ic of 100mA, Pd of 1.2W, ft of 400MHz, and Cob of just 1.4pF with medium beta available in four grades to 320.
Yup, looks good - higher Vceo, lower Ic, Ic vs. Vce slightly less ideal. Otherwise very similar to the c3953, including the SOA. It was not available locally the last time I looked, but there's bound to be some NOS available somewhere.
Yup, looks good - higher Vceo, lower Ic, Ic vs. Vce slightly less ideal. Otherwise very similar to the c3953, including the SOA. It was not available locally the last time I looked, but there's bound to be some NOS available somewhere.
AKSA said:
Yeah Hugh,
I liked his[Roender] amp very much......the drive is symmetric .....and OLG doesnot suffers that much.......
but yes in your single ended approach its not enough to get descent OLG.....
I am designing another Class-H for a client in which i would like to use folded cascode using MJE340/350 pair....
K a n w a r
> fT peaks at ~400MHz/5 mA for the c3953 vs. ~250MHz/20 mA for the c3423.
Correction: fT peaks at ~400MHz at ~40mA for the c3953 - I misread the chart earlier.
Correction: fT peaks at ~400MHz at ~40mA for the c3953 - I misread the chart earlier.
Current problem for most guys is the (local) obtainability of either one of the A1538/A1539/A1540-C3953/C3954/C3955 Sanyo beauties.
Quiz: ex-Oz politician.
Howie Who ?
Quiz: ex-Oz politician.
Howie Who ?
Jacco,
Truly ex.......
More than 5% swing to Labor, biggest since 1972 when Gough Whitlam swept to power.
However, Oppositions don't win. Governments lose. They went across to the dark side of private enterprise and upset the workers.
Watch the next four years......
Where can you buy C3600/A1406 Sanyos?
LXG,
Can you get these devices in B'lore? Is there a risk of fakes with the Sanyos? These are actually not new devices, pdf indicates Sept 2002 and I think it might be a revision.
Hugh
Truly ex.......
More than 5% swing to Labor, biggest since 1972 when Gough Whitlam swept to power.
However, Oppositions don't win. Governments lose. They went across to the dark side of private enterprise and upset the workers.
Watch the next four years......
Where can you buy C3600/A1406 Sanyos?
LXG,
Can you get these devices in B'lore? Is there a risk of fakes with the Sanyos? These are actually not new devices, pdf indicates Sept 2002 and I think it might be a revision.
Hugh
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