# Germanium Buffer Impedance

#### spoontex

Hello,

I've a lot of OC1045 GE transistors, with a very low leakage and low gain ( 20 - 30 hfe ). I've searched what to do with these transistors, and I found an article from AMZ that explains what to do with high leakage transistors.

AMZ Germanium Transistor Buffer

But I think I need to rise R4 with the OC1045.

Zin = ( B + 1 ) x R4

Supposly that I have some AC128 with 100 hfe:

Zin = ( 100 +1 ) x 10000 = 1M

but for the OC1045 with 20 hfe:

Zin = ( 20 +1 ) x 10000 = 210K

It's a bit low impedance for a buffer no?

I'm wrong?

please correct me if it's wrong.

Anybody help me to calculate the Zout?

Thanks.

Last edited:

This will help;

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#### Mark Tillotson

Hello,

I've a lot of OC1045 GE transistors, with a very low leakage and low gain ( 20 - 30 hfe ). I've searched what to do with these transistors, and I found an article from AMZ that explains what to do with high leakage transistors.
They are high frequency transistors, gain has been sacrificed in order to optimize high frequency performance (low base-collector capacitance, fast recombination?).

As for uses, I suspect that sort of transistor was picked in early logic circuitry, the low gain isn't a problem for logic, the high speed is a bonus. Ge devices can work well in single-cell (1.5V) battery-powered circuits due to the low Vbe. For a buffer application use them as Darlington pairs?

#### PRR

Paid Member
They are high frequency transistors, gain has been sacrificed... picked in early logic circuitry..........

Jon's data clearly says "IF amp in AM". The 6MHz cutoff means the working gain at IF is 10 or 15. Excess DC(/audio) gain is not needed, could trouble some radio designs, and anyway high hFE parts can be sold under another number at a higher price.

It's not "the best part" for a guitar buffer. OTOH the demand for Ge AM radios is zilch so the price for "lots" seemed attractive.

#### spoontex

Thanks a lot for the information. I think this transistors dosen't worth for a buffer. Maybe I will use them only for ge diodes.

Any other suggestion?

#### Elvee

There are much smarter ways to make a high-perf buffer from Ge transistors: this exercise has been done (successfully) 50 or 60 years ago.

The AMZ circuit is probably one of the lamest example you could find.
The PCB design hints at that too: needing two layers + PTH for such a primitive circuit is a good indicator of the sophistication level

#### PRR

Paid Member
> Any other suggestion?

"Darlington" has been mentioned twice on two forums.

#### bogdan_borko

There are much smarter ways to make a high-perf buffer from Ge transistors: this exercise has been done (successfully) 50 or 60 years ago.

The AMZ circuit is probably one of the lamest example you could find.
The PCB design hints at that too: needing two layers + PTH for such a primitive circuit is a good indicator of the sophistication level

It's not about smart way to make buffer, it's about guitar sound. When I was young, playing and didn't know much about electronics, I've made a buffer with old 741 and 9V battery that sounded great with hambucket pickup on a crappy bulgarian guitar... That sounded better than passive stratocaster, my friend had...

#### bogdan_borko

But, yes double sided pcb for this is funny.. &#55357;&#56833;

#### JMFahey

About only rewarding use for a germanium transistor is building al OLD Fuzz or the Dallas Rangemaster treble/gain booster .

Given germanium transistors are leakier than a handknit water hose, I would avoid building Darlingtons around them; high impedance and high Hfe are simply outside their league.

#### spoontex

Yes,

I agree. I only was experiment with some transistors, and what to do with this ones low gain. But definitely I prefer an opamp buffer or jfet.

Maybe I use them for a Range Master or Fuzz with darlington pair, it's a better idea I think.

#### Fast Eddie D

The original Pignose practice amplifier was built with germanium transistors. My buddy still has one from the 1960s and still uses it.