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From: Okkim Atnarivik on 26 Mar 2010 08:48
Joerg <invalid(a)invalid.invalid> wrote:
: As Tim wrote, resistors. Usually one 0402 or smaller resistor around
: 50ohms (whatever you have there) right at the base and in series with it

56ohm 0402 piggybag'd with Murata LQW15 22nH at base and collector works
nicely.

: I don't know what you want to do with those. Not having the emitter on
: ground can get very spooky. The collector can be separated by a snippet
: of copper foil as a little "wall".

Although it feels spooky, it is possible to make a long-tailed pair
out of those in a stable manner, without spoiling the noise. I didn't
need the fence, although I had to use one in the older BF862 FET-based
amplifier.

Regards
Mikko
From: Joerg on 26 Mar 2010 09:54
Okkim Atnarivik wrote:
> Joerg <invalid(a)invalid.invalid> wrote:
> : As Tim wrote, resistors. Usually one 0402 or smaller resistor around
> : 50ohms (whatever you have there) right at the base and in series with it
>
> 56ohm 0402 piggybag'd with Murata LQW15 22nH at base and collector works
> nicely.
>
> : I don't know what you want to do with those. Not having the emitter on
> : ground can get very spooky. The collector can be separated by a snippet
> : of copper foil as a little "wall".
>
> Although it feels spooky, it is possible to make a long-tailed pair
> out of those in a stable manner, without spoiling the noise. I didn't
> need the fence, although I had to use one in the older BF862 FET-based
> amplifier.
>

The BF862 is a moped against some of the new BJTs such as a BFP620, it
has an ft about 100 times higher :-)

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
From: Phil Hobbs on 26 Mar 2010 12:39
On 3/26/2010 9:54 AM, Joerg wrote:
> Okkim Atnarivik wrote:
>> Joerg <invalid(a)invalid.invalid> wrote:
>> : As Tim wrote, resistors. Usually one 0402 or smaller resistor around
>> : 50ohms (whatever you have there) right at the base and in series
>> with it
>> 56ohm 0402 piggybag'd with Murata LQW15 22nH at base and collector works
>> nicely.
>>
>> : I don't know what you want to do with those. Not having the emitter
>> on : ground can get very spooky. The collector can be separated by a
>> snippet : of copper foil as a little "wall".
>>
>> Although it feels spooky, it is possible to make a long-tailed pair
>> out of those in a stable manner, without spoiling the noise. I didn't
>> need the fence, although I had to use one in the older BF862 FET-based
>> amplifier.
>>
>
> The BF862 is a moped against some of the new BJTs such as a BFP620, it
> has an ft about 100 times higher :-)
>

But it has a 1 kHz 1/f corner, starting at a flatband value of 0.8
nV/sqrt(Hz), whereas the SiGe parts' corners are 100 kHz or higher.

Some of Mikko's noise data on those SiGe things are amazing--200
pV/sqrt(Hz)--but they kind of fall apart in the audio range.

Cheers

Phil Hobbs



--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
From: Joerg on 26 Mar 2010 12:44
Phil Hobbs wrote:
> On 3/26/2010 9:54 AM, Joerg wrote:
>> Okkim Atnarivik wrote:
>>> Joerg <invalid(a)invalid.invalid> wrote:
>>> : As Tim wrote, resistors. Usually one 0402 or smaller resistor around
>>> : 50ohms (whatever you have there) right at the base and in series
>>> with it
>>> 56ohm 0402 piggybag'd with Murata LQW15 22nH at base and collector works
>>> nicely.
>>>
>>> : I don't know what you want to do with those. Not having the emitter
>>> on : ground can get very spooky. The collector can be separated by a
>>> snippet : of copper foil as a little "wall".
>>>
>>> Although it feels spooky, it is possible to make a long-tailed pair
>>> out of those in a stable manner, without spoiling the noise. I didn't
>>> need the fence, although I had to use one in the older BF862 FET-based
>>> amplifier.
>>>
>>
>> The BF862 is a moped against some of the new BJTs such as a BFP620, it
>> has an ft about 100 times higher :-)
>>
>
> But it has a 1 kHz 1/f corner, starting at a flatband value of 0.8
> nV/sqrt(Hz), whereas the SiGe parts' corners are 100 kHz or higher.
>

I meant WRT the tendency to oscillate. They sure aren't so great to
regulate and current-steer laser diodes. For that I'd use devices such
as the BCX70K.


> Some of Mikko's noise data on those SiGe things are amazing--200
> pV/sqrt(Hz)--but they kind of fall apart in the audio range.
>

Yup, not that great for audio. Most devices aren't. I want my tubes back :-)

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
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