Dual "Matched" FETs - U441

[aziltz]

I found some U441 6-pins transistors which are labeled as matched dual FETS.

http://www.datasheetcatalog.org/datasheet/vishay/70251.pdf

Has anyone ever used these?  Would they help in phasers and such where matched components are called for?

Or perhaps its just a more compact way to make a minibooster?

[R.G.]

Would they help in phasers and such where matched components are called for?

They're generally used for differential amplifiers. They'd be good in a Phase 45 clone, maybe. For a P90 with four phase stages or phasers with more stages, you're back into matching, but now you have to match pairs against each other.

Or perhaps its just a more compact way to make a minibooster?

That works, but SRPP and mu amps like t he minibooster don't need matched FETs.

[JDoyle]

One thing - if those don't have a pin connection for the substrate you have to make sure that neither gate is applied a voltage greater than the other JFET's source - i.e. a mu-amp, unfortunately -otherwise you will turn on a parasitic SCR that will require removing to power to reset, if it doesn't burn it up first!

You can probably avoid this by connecting the CASE to the lowest voltagein the circuit.

Regards,

Jay Doyle

[DDD]

One thing - if those don't have a pin connection for the substrate you have to make sure that neither gate is applied a voltage greater than the other JFET's source - i.e. a mu-amp, unfortunately -otherwise you will turn on a parasitic SCR that will require removing to power to reset, if it doesn't burn it up first!

Is it right? The datasheet says the FETs are on the separate chips to avoid (reduce) any possible parasitics. Also, there's the same pair available in the plastic case, so what should we "ground"?

[JDoyle]

One thing - if those don't have a pin connection for the substrate you have to make sure that neither gate is applied a voltage greater than the other JFET's source - i.e. a mu-amp, unfortunately -otherwise you will turn on a parasitic SCR that will require removing to power to reset, if it doesn't burn it up first!

Is it right? The datasheet says the FETs are on the separate chips to avoid (reduce) any possible parasitics. Also, there's the same pair available in the plastic case, so what should we "ground"?

Sorry - that condition I mentioned only applies to those on the same substrate. If they are on seperate chips, all is fine, but the matching won't be as good as if they were.

Sorry for the confusion!