Germanium Transistors! Help!

[StevenStanleyBayes]

I need help with the datasheet of NTE102A and NTE103A. Attached is the datasheet.

Everything looks fine, except one thing : the datasheet says :

1.

" NTE102A (PNP) & NTE103A (NPN)
Germanium Complementary Transistors
Medium Power Amplifier "

2.

" Common-Emitter Cutoff Frequency, fαe, at VCB = 2V and IE = 10mA : 10KHz "

CAN YOU, PLEASE, EXPLAIN POINT 2. HOW CAN AN AUDIO TRANSISTOR HAVE A CUTOFF FREQUENCY OF 10KHz IN ANY CONFIGURATION AT ANY CIRCUMSTANCES?

Also :

I am extremely interested in Germanium transistors. I have found AD161 and AD162 at AliExpress, but, these are 20V.

1. I would take any NPN and PNP, even, when they are not complementary ( yet, kind of, similar, to some extent ).

2. Ideally, all voltages best be >= 40V. In case this is not possible, they must be >= 30V.

3. The current best be >= 100mA. Lower currents may be OK, such as 10mA or, even, 1mA.

4. They best be audio rated, yet, I would take anything.

5. Soviet or Russian OK.

6. Please, be kind to provide numbers. Websites are very difficult to search.

I have found some sites, again, all except NTE are difficult to search :

Germanium Transistors - Page 1 - Small Bear Electronics

Parametric Search | GP BJT | New Jersey Semiconductor

Transistors | Germanium Transistors | NTE Electronics

Comset Semiconductors - Welcome

 

[NareshBrd]

Please explain what is the use of this information.
You want to build a Germanium power amp?
Search that on many forums, must have been discussed earlier.

What will you do, suppose the item is not available, or it has a better substitute?
10 kHz is not audio use.
Maybe another forum will be helpful.

See Japanese and European part numbers.
You will not find new production Germanium devices, except maybe mil spec at fantastic prices.
Old ones may have deteriorated in storage, among the reasons they went out of use.

So, like a Don Quixote quest, searching for something not quite real.

Have fun.

 

[bucks bunny]

I am surprised the AC122 Ge Type is still available
AC122 | Vishay | Burklin Elektronik
It was in the sixties that I fiddled with these. Did not like their high noise, high cutoff current and low bandwidth. Soon replaced them by the upcoming Si-types BC109. Never went back

 

[PRR]

..." Common-Emitter Cutoff Frequency, fαe, at VCB = 2V and IE = 10mA : 10KHz "
....HOW CAN AN AUDIO TRANSISTOR HAVE A CUTOFF FREQUENCY OF 10KHz IN ANY CONFIGURATION AT ANY CIRCUMSTANCES? ....

"fαe is the frequency at which the common emitter current gain (hfe), falls to 0.707 x (mid-frequency hfe)."
BJT Cutoff Frequency and Capacitance | Junction Capacitances

Say hFE is 50 at 100Hz, nearly 50 at 1kHz, but down to 35 at 10kHz. How is that preposterous?

 

[Enzo]

And you are looking at 60-70 year old technology. We can hardly expect it to perform at modern levels.

 

[wg_ski]

So that would make it about 200kHz fT, par for the course for many Ge transistors. You *can* get them with gain at RF, but they tend to make very poor amps for driving speakers (even little bitty ones).

Early transistor tech was pretty poor - tubes were better for audio. The 6L6 has been around far longer, can be made to sound really nice, and puts out enough watts to dance to.

I do play around with Ge’s myself, but never for anything serious. Not going to spend hundreds of $ on a Ge amp project. They can be found on the surplus market from time to time and I never spend more than a buck or two. Just when I find something that looks interesting. And usually something with a bit more kick to it than the old 2SB56 (NTE102). Then I might play with it for a couple weeks, and put it aside for months/years.

 

[Mark Tillotson]

" Common-Emitter Cutoff Frequency, fαe, at VCB = 2V and IE = 10mA : 10KHz "

CAN YOU, PLEASE, EXPLAIN POINT 2. HOW CAN AN AUDIO TRANSISTOR HAVE A CUTOFF FREQUENCY OF 10KHz IN ANY CONFIGURATION AT ANY CIRCUMSTANCES?

Noone uses pure common-emitter in a low-distortion circuit anyway, this line is just saying that if you do use pure common-emitter the Miller effect will start to drop the gain by 10kHz. The same 10kHz figure is true for a 2N3055 I note.

Or put another way its best to degenerate the emitter or cascode it for voltage amplification, or better still use it as an emitter-follower driver.

 

[StevenStanleyBayes]

"fαe is the frequency at which the common emitter current gain (hfe), falls to 0.707 x (mid-frequency hfe)."
BJT Cutoff Frequency and Capacitance | Junction Capacitances

Say hFE is 50 at 100Hz, nearly 50 at 1kHz, but down to 35 at 10kHz. How is that preposterous?

This is preposterous, because, no transistor parameters must be affected at frequencies, much higher than 20KHz, regardless of what materials they are made.

Yet, your explanation of Beta ( f ) dependance is excellent and matches the explanations of many others and I thank to all.

 

[StevenStanleyBayes]

I have found Soviet or Russian, complementary, Germanium transistors GT402 and GT404. They look OK, but, can anyone provide a datasheet in any language ( Russian OK ). I was unable to easily find them.

I thank the poster for 2SB56. I will check them, yet, I am not sure there is any literature.

Please, all, provide MORE transistor numbers.

 

[StevenStanleyBayes]

I have just checked 2SB56 out. Excellent, but, the voltages are very low. Just 20V and 25V.

Also, there is a complementary : 2SD468.

The biggest problem is the Ube, which, is the same as the Silicon transistors. I need a true, Germanium, Ube.

Again the voltages are too low. Can you list some similar but, > 30V?

 

[StevenStanleyBayes]

I found something here, but, not much of a stock : GE Replacement Transistors for Sale| Talon Electronics LLC

 

[StevenStanleyBayes]

There are, also, tons of Germanium transistors on eBay, even Soviet and Russian, but, I must know the numbers and I cannot find the numbers of what I want easily. Ideally, but, not only, I am interested in :

1. Germanium.
2. Typical, low, Germanium Ube.
3. Audio ( low noise ).
4. >=30V. 40V preferable.
5. Any power >= 0.6W. Lower may be OK too.
6. Current of >= 100mA. Lower OK.

 

[StevenStanleyBayes]

Something good from the Internet :

Here is a list (name, original name, hfe according to datasheet)
Russian letters (as it goes in Russian alphabet):
А=A
Б=B
B=V
Г=G
Д=D
Е=E
И=i (I)
Ж=J (ZH)
Л=L

Etymology of names: russian letter П (english P) meant transistor (полупроводник), it's early tradition from 60-s, next - МП (english: MP), modernized transistor, and ГТ (GT) and 1T (1T) germanium transistor (tradition of naming based on transistor material).
1T (not IT!) is a kind of grade (military grade, slected etc). Sometimes even usual ge transistors (П, МП, ГТ) have a rombus marking - OTK marking or military grade, selected version.
Next appears silicon transistors - their names starts with KT (english KT) and 2T (graded version, military etc, in russian tradition - "5" ("military") acceptance).
Example of KT transistor is famous sub for 2N5088: russian KT3102E with hfe 400-1000 used in russian BigMuff's.
Numbers after letter - number of design and specifications.

GT series (ГТ)
Many of them (not all) have 1T version, wich is the same but selected, graded version, sometimes even with mentioned in datasheet higher Hfe)
GT108V (ГТ108В) - hfe 60-130
GT108G (ГТ108Г) - hfe 110-250
GT109E (ГТ109Е) - hfe 50-100
GT109G (ГТ109Г) - hfe 50-100
GT109V (ГТ109В) - hfe 50-100
GT115V (ГТ115В) - hfe 60-150
GT115G (ГТ115Г) - hfe 60-150
GT124B (ГТ124Б) - hfe 71-162
GT124V (ГТ124В) - hfe 120-200
GT308B (ГТ308Б) - hfe 50-120
GT308V (ГТ308В) - hfe 80-150
GT308G (ГТ308Г) - hfe 90-200
GT309B (ГТ309Б) - hfe 60-180
GT310G (ГТ310Г) - hfe 60-120
GT310E (ГТ310E) - hfe 60-120
GT311D (ГТ311Д) - hfe 60-180
GT311i (ГТ311И) - hfe 100-300
GT311k (ГТ311K) - hfe 60-180
GT311L (ГТ311л) - hfe 150-300
GT402B (ГТ402Б) - hfe 60-150
GT402G (ГТ402Г) - hfe 60-150
GT402E (ГТ402E) - hfe 60-150
GT402i (ГТ402И) - hfe 60-150
GT403B (ГТ402Б) - hfe 50-150
GT403G (ГТ402Г) - hfe 50-150
GT403D (ГТ402Д) - hfe 50-150
GT404B (ГТ404Б) - hfe 60-150
GT404G (ГТ404Г) - hfe 60-150
GT404E (ГТ404Е) - hfe 60-150

P series (П) seems to be old series.
Low noise GE transistors: П27, П27А, П27Б, П28 suitable for first input stage.
P27 (П27) - hfe 20-90
P27A (П27А) - hfe 20-60
P27B (П27Б) - hfe 42-126
P28 (П28) - hfe 33-100
P307B (П307Б) - hfe 50-150
P307V (П307В) - hfe 50-150
P414A (П414А) - hfe 60-120
P414B (П414Б) - hfe 100-200
P415A (П415А) - hfe 60-120
P415B (П415Б) - hfe 100-200
P416A (П416А) - hfe 60-125
P416B (П416Б) - hfe 90-200

MP series (МП)
Low noise GE transistors: МП13Б, МП39Б suitable for first input stage.
General usage, low frequency - МП21, МП40, МП41, МП42

MP21A (МП21А) - hfe 50-150
MP25B (МП21Б) - hfe 30-80
MP39B (МП21Б) - hfe 20-60
MP42B (МП42Б) - hfe 45-100
MP15A (МП15А) - hfe 50-100
MP16B (МП16Б) - hfe 45-100

The letters are given to distinguish them by Hfe, max collector-emitter voltage (like ГТ402Б (25V) and ГТ402И (40v)) etc
Many of them hard to find even in Russia (like popular ГТ402И (GT402i) which is good choice for Fuzz Factory clones).
Some of them have сomplementary types: ГТ402 (pnp) and ГТ404 (npn).

Special attention to:
* GT308V (ГТ308В)
* MP39B (МП39Б)
As per my experience they are actually low-noise and stable ones.

 

[wiseoldtech]

I've got those NTE transistors in one of my stock bins.
They were commonly used in 1960's portable pocket radios.
What use are they going to be for this repair?

 

[StevenStanleyBayes]

Here is what I have found on Soviet and Russian Transistors :

?????????? ?? ???????????? (??????????, ???????, IGBT)

GT402G - ?????????? ?? ???????????? (??????????, ???????, IGBT)
GT402V - ?????????? ?? ???????????? (??????????, ???????, IGBT)

GT404I - ?????????? ?? ???????????? (??????????, ???????, IGBT)

 

[StevenStanleyBayes]

***

 

[StevenStanleyBayes]

I've got those NTE transistors in one of my stock bins.
They were commonly used in 1960's portable pocket radios.
What use are they going to be for this repair?

I want to used them as buffers for amplifier only because of their low Ube. Thus, I need a typical for Ge Ube of, say, 0.2 to 0.4V.

1. Germanium.
2. Typical, low, Germanium Ube.
3. Audio ( low noise ).
4. >=30V. 40V preferable.
5. Any power >= 0.6W. Lower may be OK too.
6. Current of >= 100mA. Lower OK.

 

[NareshBrd]

Use FETs, small ones are easy to get, will not degrade.
Or use op amps for low Ube.

Are you female?
You took a long time to tell what you wanted to do.

 

[wiseoldtech]

I want to used them as buffers for amplifier only because of their low Ube. Thus, I need a typical for Ge Ube of, say, 0.2 to 0.4V.

1. Germanium.
2. Typical, low, Germanium Ube.
3. Audio ( low noise ).
4. >=30V. 40V preferable.
5. Any power >= 0.6W. Lower may be OK too.
6. Current of >= 100mA. Lower OK.

Forget it.
What you're asking is not good design practice.
If it were, germaniums would have been used in commerial products for that reason.

 

[mondogenerator]

I have MP37B and MP42A germanium, both HFe 40 to 80.

I even have some MP111a (which are Si, and even lower gain like Hfe 20...)