Why are BFR181 transistors so fragile?

Yikes. 20 mA abs max! It must be a really tiny chip.

Please post your schematic.

The c-b junctions of those tiny RF parts make amazing diodes.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

It's probably screaming at the top of its little voice at a few GHz for a millisecond before giving up the ghost.

Show us what you are doing, schematics and layout. We'll have a better chance at guessing what happened.

Jeroen Belleman

Good point. It might oscillate itself to death if enough power supply is available.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

Then I need a digital scope to record the process?

Since I can't attach a drawing here, this is the SPICE netlist:

• transimp simple vin 20 0 ac 1 rcalib 20 1 10k cphd 1 0 22p q1 2 1 0 mytotor rtransimp 1 4 4k ccomp 2 1 .1p vp5 10 0 dc 5 R9 10 2 5.6k Rab 3 4 1.8k Ca 3 4 100n q2 10 2 3 mytotor R11 4 11 10k vm5 11 0 dc -5 .model mytotor npn rb=4 is=1e-14 bf=150 tf=20p cje=.5p cjc=.5p

Bye,

Do you really need 8GHz transistors? There's a hefty RC lowpass right at the input.

Jeroen Belleman

And where's the output?

There doesn't seem to be enough energy available to blow up transistors.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

You're making life hard for yourself - just change the transistor symbol type to a subcircuit (X) and use the subcircuit model directly. If you change the subcircuit names to numerics you can also step through the different transistors - see below where I've changed your circuit.

(I'll upload to mega instead because the netlist will probably need manual editing otherwise.)

Yeah I know but once it's done it's easy to duplicate. I'm not getting any response from the mega link, just a continuously spinning graphic. I'll try again in the morning.

I wasn't able to download any file from the link you provided.

oops, this should be it.

oops, try this

Thank you for the very educational file. I was going to ask how you get the attribute list to show up when right clicking a newly placed npn but Google just told me it's as simple as pressing Ctrl.

A subckt to schematic converter would be nice but I can understand why that's hard.

There are netlist browsing tools available, but the free ones are pretty useless. This link is a view of the BFR193 subcircuit using a commercial tool, to show the type of schematic they generate.

Perhaps AI will help with that in the future. LCM? (Large Circuit Model).