Questions about Transistors with high beta (hfe) up to 3000 without Darl.-Topology - Page 2 - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 9th December 2011, 09:56 PM   #11
CBS240 is offline CBS240  United States
diyAudio Member
 
CBS240's Avatar
 
Join Date: Aug 2005
Location: K-town
How do these devices compare with regard to Early Voltage to lesser DC gain devices of similar Vceo?
__________________
All the trouble I've ever been in started out as fun......
  Reply With Quote
Old 10th December 2011, 09:36 AM   #12
diyAudio Member
 
tiefbassuebertr's Avatar
 
Join Date: Jul 2005
Location: D-55629 Schwarzerden
Quote:
Originally Posted by wahab View Post
Any improvement in some caracteristics will inevitably reduce the abilities
of the device in some other areas.

The Hitachi/Renesas 2SA872/2SC1775 complementary pair
has respectable gain of up to 1200 , certainly less than the super beta
devices debated above , but more certainly they have high VCE and FT ,
very low noise and are somewhat a very wise compromise in matter of global caracteristics.
Vce of 2SC1775 is 90V and from the 2SC1775A 120V
At first look large Vce values are an advantage for LTP differential amplifiers.

Most designers use the full value of Vce in their LTP stages. But there is now the disadvantage, that only small idle currents are possible (much lower than the ideal value between 3mA and 10mA) or OTOH there are burned PCB aeras after a short time of use due too excessive power dissipation in the LTP pair. The NAD 3240PE and the 306 is such an example.

Thus a high value of Vce isn't realy an advantage.

By several amps I introduce resistors in the collector line, so that in real life the VCE value is at maximum only 20V without any disadvantage in respect to the other parameters. As consequence I can enhance the idle current to higher values without trouble (I prefer 3mA - 5 mA instead the often used value between 0,1mA and 1mA).

Last edited by tiefbassuebertr; 10th December 2011 at 09:44 AM.
  Reply With Quote
Old 10th December 2011, 11:46 AM   #13
Account disabled at member's request
 
Join Date: May 2006
Quote:
Originally Posted by wahab View Post
Any improvement in some caracteristics will inevitably reduce the abilities
of the device in some other areas.

The Hitachi/Renesas 2SA872/2SC1775 complementary pair
has respectable gain of up to 1200 , certainly less than the super beta
devices debated above , but more certainly they have high VCE and FT ,
very low noise and are somewhat a very wise compromise in matter of global caracteristics.
In practice youll never find such high gain with 2SA872/2SC1775, Ive used thousands of these pairs and never once found any showing an hfe higher than 350 while its not very hard to find mpsa18 with hfe approaching
700 at around 3 ma mark which is a value often used in LTPs. As regards Ft many super beta s are superior to 2SA872/2SC1775, vce is the only weak spot.
  Reply With Quote
Old 10th December 2011, 11:55 AM   #14
Account disabled at member's request
 
Join Date: May 2006
Quote:
Originally Posted by CBS240 View Post
How do these devices compare with regard to Early Voltage to lesser DC gain devices of similar Vceo?
They are worse off but the advantage is when you use them in cascode circuits. This way you create a super BJT, very high gain, high early voltage. If used within their vce limits they can actually be a contribute for those that like to manipulate THD spectrum depending on the position they are used. A lower early voltage will in all cases contribute to higher THD but this is in respect of 2nd harmonics which some delibertly want to create.
  Reply With Quote
Old 10th December 2011, 01:40 PM   #15
diyAudio Member
 
Join Date: Nov 2007
Location: Dallas
I threw a quad of MPS18 at the front end of an MC2100.

Matched to each other (on a $2 harbor freight meter) in
the 651-655 zone. Another "identical" $2 meter thought
the same set were all about 630...

The worst part was the HFE socket was fake. Just some
guide holes. Had to push the wires against pads on the
meter PCB, very hard to get all three in contact at once.

The PNPs I chose were all 315 on the dot, both meters.

Last edited by kenpeter; 10th December 2011 at 01:50 PM.
  Reply With Quote
Old 10th December 2011, 04:54 PM   #16
diyAudio Member
 
Join Date: Dec 2005
Location: Kuala Lumpur
Quote:
Originally Posted by tiefbassuebertr View Post
By several amps I introduce resistors in the collector line, so that in real life the VCE value is at maximum only 20V without any disadvantage in respect to the other parameters. As consequence I can enhance the idle current to higher values without trouble (I prefer 3mA - 5 mA instead the often used value between 0,1mA and 1mA).
Which is the advantage of very high hfe, 5mA would have very high Ib for a hfe=200 device
  Reply With Quote
Old 10th December 2011, 05:19 PM   #17
diyAudio Member
 
tiefbassuebertr's Avatar
 
Join Date: Jul 2005
Location: D-55629 Schwarzerden
Quote:
Originally Posted by davidsrsb View Post
Which is the advantage of very high hfe, 5mA would have very high Ib for a hfe=200 device
I start this thread to get answers to this question (read questions from post #1).
  Reply With Quote
Old 10th December 2011, 05:31 PM   #18
diyAudio Member
 
Sch3mat1c's Avatar
 
Join Date: Jan 2003
Location: Milwaukee, WI
Send a message via ICQ to Sch3mat1c Send a message via AIM to Sch3mat1c
Add to the list: 2SC1273. 30V, 2A, hFE > 500, TO-220FP package.

Although it does saturate very easily, it switches very slowly, on par with TIP31 and other general purpose power transistors, regardless of base drive current. I expect the doping profile or charge distribution or junction capacitance or something on these devices is such that they always slow way down as they begin to saturate.

Speaking of base drive current, don't be fooled by the high gain, which is a DC parameter. The AC impedance will be much lower, because the base has considerable capacitance and charge storage.

Tim
__________________
Seven Transistor Labs
Projects and Resources
  Reply With Quote
Old 10th December 2011, 11:02 PM   #19
diyAudio Member
 
tiefbassuebertr's Avatar
 
Join Date: Jul 2005
Location: D-55629 Schwarzerden
Quote:
Originally Posted by Sch3mat1c View Post
Add to the list: 2SC1273. 30V, 2A, hFE > 500, TO-220FP package.

Although it does saturate very easily, it switches very slowly, on par with TIP31 and other general purpose power transistors, regardless of base drive current. I expect the doping profile or charge distribution or junction capacitance or something on these devices is such that they always slow way down as they begin to saturate.

Speaking of base drive current, don't be fooled by the high gain, which is a DC parameter. The AC impedance will be much lower, because the base has considerable capacitance and charge storage.

Tim
This is the outline of 2SC1273, from which I have heard:
2SC1273, Tube 2SC1273; Röhre 2SC1273 ID40038, Transistor
Can you upload genuine NEC datasheet (also from 2SC1271 and 2SC1272) ??
I haven't success to find this online.

Last edited by tiefbassuebertr; 10th December 2011 at 11:05 PM.
  Reply With Quote
Old 11th December 2011, 05:13 AM   #20
diyAudio Member
 
Sch3mat1c's Avatar
 
Join Date: Jan 2003
Location: Milwaukee, WI
Send a message via ICQ to Sch3mat1c Send a message via AIM to Sch3mat1c
Oh, my mistake it's 2SD1273!

Short form spec from datasheetarchive:
Quote:
V(BR)CEO (V)=80
V(BR)CBO (V)=100
I(C) Abs.(A) Collector Current=3
Absolute Max. Power Diss. (W)=2
I(CBO) Max. (A)=100u
@V(CBO) (V) (Test Condition)=80
V(CE)sat Max.(V)=1
@I(C) (A) (Test Condition)=2
@I(B) (A) (Test Condition)=50m
h(FE) Min. Static Current Gain=1.2k
h(FE) Max. Current gain.=2.5k
@I(C) (A) (Test Condition)=500m
@V(CE) (V) (Test Condition)=4
f(T) Min. (Hz) Transition Freq=50M
@I(C) (A) (Test Condition)=200m
@V(CE) (V) (Test Condition)=12
Package=SOT-186
Surprisingly Vce(sat) is tested at only 40 hFE, however it will gladly do the same with much less base current. It starts to look like a FET with Vgs(th) = Vbe, in that you hardly need any current to drive it -- enough that, whatever peak capacity a gate drive source would supply (even logic level), it's more than enough to turn this thing on.

Tim
__________________
Seven Transistor Labs
Projects and Resources
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
measuring hfe / beta gain Parts 10 12th October 2013 02:43 PM
Matching transistors - Measuring hfe TomWaits Solid State 118 3rd March 2007 07:22 PM
Need low power high beta transistors - please drop me a few part numbers... peufeu Solid State 37 3rd November 2006 01:22 AM
Confused over hfe variation in BC559 transistors Beggar Parts 5 29th September 2002 07:13 AM


New To Site? Need Help?

All times are GMT. The time now is 11:21 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2