[sdiy] MC1495 multiplier chip discontinued completely

[Czech Martin]

I just learned from Arrow/Spoerle that the MC1495 multiplier chip
is discontinued and they can not ship any more.
On Semiconductor has accordingly made an update to their
web site. 

So I guess the 1495 is *really* gone.

The good thing about this chip was that it contained more
or less matched transistors for the gain cell, so offset and offset
drift was under control. I.e. carrier suppression was good.
Compander circuits will not make a good job for this carrier
suppression, because it is not a wide band noise problem,
but very narrow, so masking is poor.

And it had an input linearisation circuitry for the 
carrier input, in order to have quite linear behaviour.
The (still available) 1496 is designed for square wave
carrier and has of course no input linearisation.
So you have to use low carrier amplitude (noise)
or accept excessive sidebands (distortion, intermodluation).
Also the 1495 allowed to taylor the gain cell bias current.
For good S/N you need a lot of current.
Most other integrated multipliers do not allow for bias
current change and are designed for low power consumption,
so S/N of 80 dB will be the upper limit, and most devices
will not even give that (AD633 for example).
For some applications this is still too much noise.

I want low noise and linear behaviour (smooth sound).
So next I try the RC4200 (?) and the 1496 with external DIY
linearisation stage. If this doesn't work I'll go back to
a complete discrete design, perhaps using a couple of
japanese dual NPN, glue, expoxyd ... whatever it takes
to cope with the offset problems...


m.c.