PING: John Larkin

Cheers. Unfortunately I don't have that one.

NT

That chapter always annoyed me. He did say that in his opinion there were 24 (or was it 26?) useful two transistor circuits, but the bugger never listed them.

As an exercise left to the reader I don't think I could ever think of more than about 18.

I looked up that chapter after this thread started... nothing there but FUNDAMENTALS of Bipolar transistors, which most 'engineers' still don't understand... essential knowledge necessary to properly design I/C's. ...Jim Thompson

Let's see.

NPN 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 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)

That's 17, so 34 with both polarities.

NPN+PNP:

NPN CE + PNP CE NPN CE + PNP follower PNP CE + NPN CE PNP CE + NPN follower PNP follower + NPN follower NPN follower + PNP follower NPN follower + PNP CE PNP follower + NPN CE PNP follower + NPN CB NPN follower + PNP CB

Sziklai (PNP input) Sziklai (NPN input) Complementary follower output stage (B->B & E->E) R-R complementary amp (B->B & C->C) Folded cascode (NPN input) Folded cascode (PNP input) 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) NPN CB -> PNP CE NPN CB -> PNP CC NPN CE -> PNP CE PNP CE -> NPN CE

That's 56, not counting FETs. Any others?

(I expect that Gilbert wasn't double-counting NPNs and PNPs, but it's still 28.)

Cheers

Phil Hobbs

Whoops, double-counted the NPN/PNP CE cascades. So 54 for both polarities, 27 counting NPN and PNP as the same.

Cheers

Phil Hobbs

Then there are all the circuits containing diode-connected transistors:

Series diodes Follower with diode drop compensation...

Cheers

Phil Hobbs

Pseudo SCR.

Schmitt trigger.

A couple of voltage regulators.

Several multivibrators... flipflop, astable, one-shot

Uni-shot.

Single-input totem pole inverter (needs a diode).

Miller ramps.

Logic inverter.

Logic buffer.

Logic delay.

Avalanche pulsers.

Voltage reference (B-E zener plus junction drops.)

Voltage references (Vbe based)

Linear amp, unbuffered and buffered

Amp with zero input threshold.

Single-transistor current sources

Blocking oscillators

Colpitts, Hartley, etc oscillators (need inductors)

Probably lots more.

Gilbert says that there's "about twenty-four" really useful circuits that can be made from two transistors. Did anyone mention these?

single balanced mixer [1] flip-flop VFO buffer [2] low noise oscillator [3] multivibrators [4] Schmitt trigger [5]

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Thank you,

if you count PNP and NPN versions only once both Sziklai option only count as one also etc.

I think you missed the one that works like a SCR, and the dual that works like a PUT

| --EBC ebc--

Both legit.

That's on the list already: CE + follower

CC + CB (unbalanced diff pair)--on the list already

Both dual CE with feedback, but they can slide. ;)

Where did the name "multivibrator" come from, anyway?

Cheers

Phil Hobbs

John L mentioned those ones.

Cheers

Phil Hobbs

oops.

| --EBC cbe--

Several logic gates.

Right, the PUT is really a PNP-NPN combination, essentially an SCR with an upper gate. It might be tricky to get the trigger and turnoff currents right.

Your earlier followup was accidentally overlooked by me. So here it is:

Pseudo SCR. Schmitt trigger. A couple of voltage regulators. Several multivibrators... flipflop, astable, one-shot Uni-shot. Single-input totem pole inverter (needs a diode). Miller ramps. Logic inverter. Logic buffer. Logic delay. Avalanche pulsers. Voltage reference (B-E zener plus junction drops.) Voltage references (Vbe based) Linear amp, unbuffered and buffered Amp with zero input threshold. Single-transistor current sources Blocking oscillators Colpitts, Hartley, etc oscillators (need inductors)

This feels somewhat like a /nuanced/ trip down memory lane. Did anyone mention these two transistor power circuits?

Power converter [1] Power inverter [2]

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Thank you,

Good point. We left out Jim Williams's fave Royer converter. Added to the list.

Cheers

Phil Hobbs

Jim Williams favourite inverter - based on the number of application note he wrote about it - was actually the Baxandall class-D sinewave inverter

Jim Williams did call it a Royer inverter, but Royer inverters generate square waves. You have to add an extra inductor - as Jim Williams did - to get sine waves out of them.

Both are two-transistor inverters.