400-500V TO-92 etc npn / pnp BJT ?

[Eeyore]

It's a bit more than the usual voltage. The MPSA44 / 94 JUST makes it
but the datasheet doesn't give hFE @ low Vce and the '94 seems to be
rare.

Any other candidates ? Cascoding could be problematical in this
application due to volt drop ( I need a current source of about 6mA
capable of handling a high voltage but with a low 'drop-out' voltage ).

Other packages could be OK but I may need TO-92 at least for dissipation
reasons.

Graham

 

[Spehro Pefhany]

It's a bit more than the usual voltage. The MPSA44 / 94 JUST makes it
but the datasheet doesn't give hFE @ low Vce and the '94 seems to be
rare.

Any other candidates ? Cascoding could be problematical in this
application due to volt drop ( I need a current source of about 6mA
capable of handling a high voltage but with a low 'drop-out' voltage ).

Other packages could be OK but I may need TO-92 at least for dissipation
reasons.

Graham

NPN:-

ST STX-616
Fairchild KSP44TA
C1573

PNP:-
Zetex ZTX560





Best regards,
Spehro Pefhany

 

[Eeyore]

NPN:-

ST STX-616
Fairchild KSP44TA
C1573

PNP:-
Zetex ZTX560

Thanks. The current gain of the Zetex part is nicely high and of course
saturates well too. It has an npn near direct complement the ZTX458 too.

Graham

 

[Eeyore]

Apex PA94 op amp with 450 volt power supplies wired as a current source.

Does it also work at 4V ? It sound expensive too.

Graham

 

[Eeyore]

4volts for output or supplies? From negative to positive swing of the opamp.

I think you misunderstood the question. I can do discrete design. I just
modelled what I wanted with Spehro's advice and My God it's good. Little change
in current ( as far as it matters ) from 2V to 400V.

Graham

 

[Eeyore]

build it with a negative supply for the low side of your current source then
you can go down to zero volts or negative.

No need in this application and no negative supply. It also has to be cheap.

Graham

 

[Eeyore]

Thanks. The current gain of the Zetex part is nicely high and of course
saturates well too. It has an npn near direct complement the ZTX458 too.

Follow-up. Zetex kindly sent me 10 samples of each by courier despite the fact
that Farnell stock them too.

All credit to Zetex.

Graham

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my email address