Fast transistors?

[jan.didden]

Hi,

I'm looking for complementary transistors, small signal (say ~1W Pc), Vce min 120V. They MUST have very low capacitance / very wide bandwidth. I'm trying to push a Vas stage to 20MHz open loop. I'm looking at less than 10pF Ccb...

Any ideas?

Jan Didden

 

[Jan Dupont]

2SA1540/2SC3955 would have been suitable if it was not for the 1W Pc and the fact that they are very hard to get as Sanyo brand

But look towards video applications......

 

[roender]

2sa1360/2sc3423
ft 200Mhz at 5mA Ic !!!
2.5pF Cob

 

[jacco vermeulen]

2sa1360/2sc3423

aka 2SA1145/2SC2705 with a heatsink.

 

[lineup]

Hi, I'm looking for

- complementary transistors,
- small signal (say ~1W Pc),
- Vce min 120V. They MUST have very
- low capacitance / very wide bandwidth.

I'm trying to push a Vas stage to 20MHz open loop. I'm looking at less than 10pF Ccb...

This is not easy, I would say.
You could find higher voltage fast transistors. Suitable.
But the hook may be Complementary NPN-PNP.
This would reduce your options the most.

Of course there are not so many fast at 1 Watt (as it is at 0.5 Watt).
I would look for VIDEO Transistors.
They usually can take higher volts and they are fast.
But video not often come in complementary pairs.

The best VAS transistors I have seen mentioned in forum
are some complementary Panasonic devices.

 

[lineup]

We have had some good topics on VAS transistors.
With good suggestions

Try this www.google.com search:

site:[url]www.diyaudio.com[/url] vas transistors

Direct link:
Google search VAS transistors

 

[jan.didden]

We have had some good topics on VAS transistors.
With good suggestions

Try this www.google.com search:

site:[url]www.diyaudio.com[/url] vas transistors

Direct link:
Google search VAS transistors

Thank you lineup, I wasn't aware that you can search this way with Google in diyaudio! I always used the internal forum search which is less than perfect...

Jan Didden

 

[syn08]

2SC3601/2SA1407 from Sanyo.

The best money can buy, not cheap or easy to find though. Used in the PGP amp, they have Ft=400MHz.

 

[jan.didden]

2SC3601/2SA1407 from Sanyo.

The best money can buy, not cheap or easy to find though. Used in the PGP amp, they have Ft=400MHz.

Yes, very good! There are others that are similar, so I guess the final selection should be price & availability.

Thanks,

Jan Didden

 

[jacco vermeulen]

If you like the A1407/C3601 and 120V will suffice, you are going to love the 2SA1538/C3953.
50-60 €ct, for example : Cricklewood in the UK should have them.

 

[roender]

... you are going to love the 2SA1538/C3953.
50-60 €ct, for example : Cricklewood in the UK should have them.

You have to pump much more current (20-30mA) through 2SA1538/C3953 to have high ft ... at 5-6mA ft is the same as 2sa1360/2sc3423 or SA1145/2SC2705.

 

[Nico Ras]

Hi,

I'm looking for complementary transistors, small signal (say ~1W Pc), Vce min 120V. They MUST have very low capacitance / very wide bandwidth. I'm trying to push a Vas stage to 20MHz open loop. I'm looking at less than 10pF Ccb...

Any ideas?

Jan Didden

Hi Jan,

Hi Jan,

I am sorry if I speak out of turn and offer not quite what you are looking for but something you may want to toy with and works very well in an audio aplications.

Now these transistors are not nearly the voltage that you are looking for (30V), but have sucessfully used them not so very long ago in a commercial application that measured beyond expectation.

The 2N5943 and 2N5583 are not complimentary pairs but they work really well together. Ccb is a respectable 1 -2 pF and Ft around 2.4 GHz Hfe is around 200. Dissipation is 2 watt.

Nico

 

[jan.didden]

Re: Re: Fast transistors?

Hi Jan,

Hi Jan,

I am sorry if I speak out of turn and offer not quite what you are looking for but something you may want to toy with and works very well in an audio aplications.

Now these transistors are not nearly the voltage that you are looking for (30V), but have sucessfully used them not so very long ago in a commercial application that measured beyond expectation.

The 2N5943 and 2N5583 are not complimentary pairs but they work really well together. Ccb is a respectable 1 -2 pF and Ft around 2.4 GHz Hfe is around 200. Dissipation is 2 watt.

Nico

Hi Nico,

Yes, they are quite good, but that Vce=30V is really too low. I can cascode them but I think I will reach the point of diminishing returns then.

Jan Didden

 

[jan.didden]

You have to pump much more current (20-30mA) through 2SA1538/C3953 to have high ft ... at 5-6mA ft is the same as 2sa1360/2sc3423 or SA1145/2SC2705.

Yes I need to spoend some time going through all those data sheets carefully. There a bit of hidden 'gotcha's'...

Jan Didden

 

[jacco vermeulen]

much more current

Mihai,

same applies to the A1407/C3601, no ?

 

[syn08]

If you like the A1407/C3601 and 120V will suffice, you are going to love the 2SA1538/C3953.
50-60 €ct, for example : Cricklewood in the UK should have them.

Unfortunately 120V is (also assuming a healthy safety margin) is very close to the limit for 100W/8ohm with MOSFET outputs...

Also try to find 2SA1406/2SC3600. Slightly lower ICmax, slightly lower Cob, same Ft=400MHz and half the price (at least 2SC3600, here in NA).

 

[Michael Chua]

Philips TO-126 Video BFQ232A; BFQ252A

Not quite 120V but fT=1.2GHz; Ccb =2.5pF. Problem is low hFE = 30 TYPICAL. Good excuse to darlington them.

 

[jcx]

and for something different:

http://www.zetex.com/3.0/pdf/ZVN0545G.pdf

sot223 can readily handle 1W, lead spacing bigger than to-92

mosfet also has "infinite" Hfe - can give more gain thru audio band

 

[syn08]

mosfet also has "infinite" Hfe - can give more gain thru audio band

Yep, and more nonlinear Cgd compared to the bipolar Cob. Plus no matched P channel pair.

 

[Lumba Ogir]

Jan,
are you gonna bring out that fast circuit (to be strongly criticized)?