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3N35 tetrode transistor question

I've been playing with some archaic transistors & devices and came across a couple of 3N35 transistors in my junk box. I do have a TI data book with pin-out and data, but have no examples on biasing and otherwise applying them. This is a four lead transistor having two base connections. I did find one source that said typically, "a few" volts bias is applied between the base leads.

How does one bias these things? And after applying voltage between the two bases, is one base driven just as in a "normal" BJT? Should the two bases have RF isolation between them? Or alternately, should they have a coupling capacitor?

This all started when a guy on a ham list described a 50mw transmitter he built using two 2N35 ("2", this time) audio transistors. Despite the low Ft, he was able to operate them at 3.5 Mc/s. I built a similar transmitter using two 2N404s. Now I have a tunnel diode crystal oscillator working, but would like to work in the 3N35 to boost it up before having a stage or two of 2N404.

Regards,

Nick

Reply to
kennnick
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The extra base junction is used to back bias most of the E-B junction. The rest of it is straight forward.

Yes.

No. The extra one should be bypassed to the emitter voltage, ground or left alone.

Reply to
MooseFET

Been a few daze since i have seen them; never messed with them, tho. I think they are the equivalent of two FETs in series, and thus are biased with the "lower" gate in standard fashion - nominally as an amplifier or oscillator. The "upper" gate is biased WRT an imaginary drain voltage for the "lower" FET; so in the case of the "lower" FET is an amplifer,the "upper" one is the cascode stage; if the "lower" FET is an oscillator, then the "upper" one can be an RF input stage to make the pair act as a mixer. At least that was my crazy impression at the time, without looking at any data or app info...

Reply to
Robert Baer

The 3N35 was indeed an NPN silicon bipolar tetrode from TI, not a fet. The same base was contacted in two locations, something possible in alloy structures where the base was formed by the bulk material. Similar parts were made by GE.

Tertrode j-fets and mosfets were registered with JEDEC from 3N89 and upwards.

RL

Reply to
legg

Same ideas can be used...

Reply to
Robert Baer

As luck would have it, I have just come across an article describing them: "Transistors" - Part 10 by Thomas Roddam Wireless World Nov 1953 P245-246

They were invented by Wallace Schimpf & Dickens and a paper on them was published in Proc. I.R.E. Vol.40 P1395 Nov 1952

Their main use was visuallised as video amplifiers with bandwidths up to the incredible figure of 130 Mc/s in the early experimental models. I have copied their circuit to:

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Reply to
Adrian Tuddenham

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