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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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30th Apr 2021, 8:44 am | #21 | |
Octode
Join Date: Jul 2009
Location: Carmel, Llannerchymedd, Anglesey, UK.
Posts: 1,509
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Re: Germanium transistor, connections reversed?
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30th Apr 2021, 1:10 pm | #22 |
Octode
Join Date: Sep 2020
Location: Thetford, Norfolk, UK.
Posts: 1,743
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Re: Germanium transistor, connections reversed?
When I started this thread, I thought someone would come back and say I was mad and had clearly tested the transistors incorrectly.
It has been very interesting reading everyone's experiences. |
2nd May 2021, 2:25 pm | #23 |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,993
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Re: Germanium transistor, connections reversed?
Germanium technlogy is alive and well in active devices. Defined as an alloy of Silicon and Germanium with Carbon the resulting transistors have an fT of 40 - 50GHz, although some of them (eg BFP840FESD) have an fT of an eye-popping 85GHz. They have a tiny Vceo of a few volts however. Astonishingly these phenomenal devices are about 30p each.
SiGe part of the core technology in Croy and Tektronix oscilloscopes, which currently go from DC into the high tens of GHz. I expect that they have to be handled with kid gloves to prevent them from being damaged by excess voltage though! Craig |
2nd May 2021, 3:01 pm | #24 |
Dekatron
Join Date: Sep 2010
Location: Cheltenham, Gloucestershire, UK.
Posts: 3,077
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Re: Germanium transistor, connections reversed?
Yes, Germanium is still in widespread use today. A few years ago I designed a quick and dirty 50mW LO amplifier for use across 5.8-6.0GHz using a similar SiGe (Silicon Germanium) part. I think it was the BFP650F and it has an Ft of 42GHz.
https://www.infineon.com/dgdl/Infine...690f03d9ba3932 The amplifier only runs at about 3V but the 1dB compression point at 5.9GHz was over +17dBm (50mW) when measured on a lab power meter. There's a few old pictures of the 6GHz prototype amplifier below. It was designed using Eagleware Genesys and Sonnet EM software and with these tools the whole PCB layout is part of the initial simulation. When the first prototype was milled it showed very similar performance to the simulation.
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2nd May 2021, 3:35 pm | #25 |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,993
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Re: Germanium transistor, connections reversed?
Now that is impressive!
Is that a ceramic board? Craig |
2nd May 2021, 8:43 pm | #26 | |
Dekatron
Join Date: Sep 2010
Location: Cheltenham, Gloucestershire, UK.
Posts: 3,077
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Re: Germanium transistor, connections reversed?
Thanks! Yes, it does contain ceramic material and the manufacturer describes it as below
Quote:
I always assumed that it is risky to reverse the connections to Si BJTs because the base-emitter junction will usually have a lower voltage and current rating. Are there some Ge parts that don't have this limitation?
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Regards, Jeremy G0HZU |
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2nd May 2021, 11:19 pm | #27 |
Dekatron
Join Date: May 2010
Location: Greater Manchester, UK.
Posts: 18,724
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Re: Germanium transistor, connections reversed?
No one has mentioned the UJT, which, if I remember correctly, is intrinsically symmetrical.
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