Hi all,
I have been working with Germanium transistor since about 1960 – as one of my several hobbies. The history with their different techniques was very diverse since 1948: point contact / grown junction / alloy junction / diffusion alloy / drift / surface barrier / mesa / etc., even npn symmetric*.
Every production process had a special goal, so every “type class” had advantages – except temperature, as Frank mentioned. I love the “old” outlines, no plastic, no uniform look. So I am collecting even the very first pocket radios since 1954 with the TO-22 outline from Texas Instruments, Hitachi and Sony. Furthermore the glass versions like OC44 … OC75 or OC602 … OC614. And these transistors are still working very good since that time without problems.
Germanium npn transistors in glass case were the OC139…OC141, described as symmetric* and could be replaced in some applications by two diodes (…?). Philips designed some pocket radios with the OC140 and OC74 as complementary push-pull output stage with OC75 as driver and a subminiature hearing aid transistor OC59 as pre-amplifier. Looking into such radios I must always laugh… that’s the diversity I like – heaven knows why. The look into radios since 1970 is most boring to me.
This very special amplifier is since many years the last active Lectron block in my superhets with pnp types:
The 1-transistor-reflex-superhet I introduced a while ago was another good example for the very special usage of (selected) germanium AM BC pnp transistors – only some Japanese types (drift types ?) worked without changing the bias resistor (or other parts of the circuit). European types only very few with some changes, Russian types were very “special”: extreme amplification / sensivity, oscillation etc.
The germanium transistors in the Lectron blocks (AF: AC173, AC151 and RF: AF126) with the built-in bias resistor may be bypassed by using the (universal) transistor blocks with a socket. Then npn or pnp, Ge or Si, RF or AF, low power or medium power types may be used depending of the actual problem / circuit.
In this photo from ~ 1970 Max Guerth used in this experiment a couple of this socket blocks:
Silicon types are always first choice, but in circuits / models / applications before ~ 1970 I like to go “old” – with all pro’s and con’s.
Best,
G.
- This reply was modified 4 years, 11 months ago by Guenther.
- This reply was modified 4 years, 11 months ago by Guenther.