We (and our customers) have built several million radios using a section of
74AC02 or 74LVC02 gate as an rf amplifier in a tripler going from around 100
MHz to 300 MHz.

It works great and is incredibly compact and cheap for the application, but
it's definitely not for the faint of heart.

It took extensive Monte Carlo simulations plus a lot of bench time to get it
right so that production yields were acceptable, and every time the
manufacturer does a die shrink or makes any process change, it all has to be
done again.  For different manufacturers, it usually requires a change in
some of the biasing resistors, so a second source is possible, but requires
a separate bill of materials to cover the changes to other components, not
to mention all the extra testing to assure that FCC compliance hasn't been
compromised.

I would say that it would take many many thousands of units for the few
cents savings per unit to recover the added engineering costs over using a
chip that was designed to be an amplifier.

> -----Original Message-----
> From: Alan B. Pearce [mailto:A.B.Pearce@RL.AC.UK]
> Sent: Friday, January 05, 2001 7:21 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [EE] : amplifier using hex inverter ??
>
>
> Using digital chips as linear devices is best left to using
> them as oscillators
> in microprocessors. You will find that almost every micro has
> a single gate set
> up for exactly this use. trying to use them as general
> purpose linear devices is
> almost bound to produce tears of frustration as there is no
> temperature
> stabilization in the linear region, and no characterization
> of gain. It may even
> be that various characteristics of the active devices are
> chosen limit the
> ability to operate in the linear region, except where the
> gate is being built in
> as an oscillator.
>
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