So it seems like this should have its own thread. From the JL thread, I've collected the following. I've edited it a bit, and tried to avoid NPN/PNP duplication. Different feedback arrangements seem a reasonable thing to allow, by analogy with "op amp circuits", where feedback is about the only thing you get to play with. NPN only or PNP only: CE cascade Darlington CE + follower CB + follower Cascaded follower CB cascade (e.g. double-section cap multiplier) Follower + CE Follower + CB (unbalanced diff pair) True diff pair Current mirror Cascode Bootstrapped cascode Follower + tail current source CE + tail current source (e.g. for AC-only amplification) Bootstrapped CB (e.g. in TIAs) White follower Two-terminal current limiter Totem pole (needs differential drive, so may be cheating) CE with current source load CB with current source load Series pass with n x Vbe voltage reference Series pass with zenered BE junction reference Back-to-back BE junction zener voltage clipper Parallelled diode-connected transistors for low voltage clipper Zenered BE + CE (overvoltage indicator) Temperature compensated zener (zenered BE with diode-connected in series for TC) RTL NOR gate RTL NAND gate Monostable Bistable Astable Schmitt Miller ramp generator Phase splitter plus follower CE with diode to cancel out input offset CB, likewise Temperature compensating current source (mirror with an emitter resistor in one side) NPN+PNP: NPN CE + PNP CE NPN CE + PNP follower NPN follower + PNP follower NPN follower + PNP CE NPN follower + PNP CB Sziklai PNP wraparound (shunt feedback to NPN emitter) Pseudo-SCR Complementary follower output stage (B-B & E-E) R-R complementary amp (B-B & C-C) Folded cascode Various level shifters: PNP CB - NPN CE (e.g. in HV RRO output stages) PNP CB - NPN CC (e.g. in HV non-RRO output stages) Single-input totem pole inverter (needs a diode). So that's 51...

Oh boy, I'd have to look up at least 1/2 of those. OK as my meek offering I just made up the silliest two transistor circuit. (do they have to be something useful?) (low voltage) bridge rectifier, pnp on top, npn on bottom... AC applied to C and E's, DC taken from the bases. it uses the silly model of a transistor as two diodes. George H.

any idea how many we got so far? NT

On a sunny day (Wed, 20 Sep 2017 16:48:09 -0700 (PDT)) it happened wrote in : And the tunnel diode osscillator, fewer parts needed.

Two-transistor circuits--can we get to 100?

Aug 30, 2017 89 Replies

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Tom Del Rosso 8 years ago

This thread can't die until the site is up. :)

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tabbypurr 8 years ago

any idea how many we got so far?

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dagmargoodboat 8 years ago

Super-regen receiver / detector?

(It's not clear whether we're counting only distinct topologies, or the same basic circuit connection adapted to different problems, e.g. a "Darlington electrometer" == or != "Darlington," == or != "Nuclear War detector" ?(*)

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Cheers, James Arthur

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John Larkin 8 years ago

I made a thermal IR detector when I was a kid. It was a black 2N107 germanium transistor in a flashlight reflector, biased at the edge of thermal runaway. It sensed my hand from three feet away.

John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com

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sroberts6328 8 years ago

I'm a big Rod Elliot fan..

Scroll three quarters of the way down for a semi-balanced two transistor NIC oscillator that is neat and uses an external RC...

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Steve

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sroberts6328 8 years ago

Turns out the above reference is US pat US2852680 by Arthur Radcliffe

Steve

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John Larkin 8 years ago

I built a battery-powered 2-terminal -1K resistor as an EE project, pretty much like fig 6 there. It was fun to play with.

John Larkin Highland Technology, Inc lunatic fringe electronics

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Jan Panteltje 8 years ago

On a sunny day (Wed, 20 Sep 2017 16:48:09 -0700 (PDT)) it happened snipped-for-privacy@gmail.com wrote in :

And the tunnel diode osscillator, fewer parts needed.

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krw 8 years ago

In our "Pulse Techniques" class in college, we analyzed multivibrators as negative impedance devices.

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Tom Del Rosso 8 years ago

IDK but this thread can't die until the site is up. :)

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