> 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.
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
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
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
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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