Sunday, September 20, 2020

Final thoughts on the PCT

 Millivolt in millivolt out not very impressive?

Look at the current! Microamps in and milliamps out. There has been many who deny the transistor being a current amp. They say it is a voltage amp. Others say it is a power amp. Ohm's law relates voltage, current and resistance. It is a matter for others to argue. Anywho, I added R2 so you can see Q1 base current is microamps.

The circuit is a common base amp direct coupled to a common collector amp.

I redrew it to show the 2 stages. 

In the days of hollow state amplifiers we used "those amplifying transformers". The interstage transformers were step up. With the high input Z amps they could boost the signal with the transformer. Notice T100 is 5:1. This boost the current. Since the PCT is a current driven device this is a good thing. Microamps in milliamps out.

Another amp I had on file.

The three junction transistor or remote base transistor compared to the PCT.

Here we have the SCR structure. Interesting? In another time we also had the SCS which is the same structure with two gates. By adding an anode gate we could have a PUT which is another interesting device.

And now the SCR equivalent with discretes. Look familiar? My PCT discrete is the inverse. PNPN rather than NPNP. The pinout is different too. Can you see it?

It would appear grounding the gate and driving the cathode with proper battery polarity should produce an amplifier? The semiconductor doping would be different but it could be a fun experiment.

EDIT: The simple two stage receiver is such low part count it could be a weekend project to wind a couple transformers and build it. Just two PCT transistors or two pair of Ge BJTs. A couple of AF output transformer could work?
What would the turns ratio be for an 800:32 ohm earbud transformer?

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