AW: Four multipliers for frequency shift

[Haible_Juergen#Tel2743]

> why not use two LM13700 to make four four-quadrant multipliers.
> If the linearisation diodes are used then the four-quadrant operation
> works independent of temperature unlike the 3080 multiplier.

Are you sure ?? Fully temperature compensated ?


> If the linearization diodes are used the circuit is similar to 
"linearized"
> Gilbert-cell with some extra current-mirror in the output.

It's not the same! The linearisation only works with *current* sources
to the diodes. The usual voltage-source + resistor-in-kOhms-range
is a rather bad approximation for a current source.

> Benefit from this circuit: a four quadrant multiplier without trimming.

I don't believe that. One word: Offset voltages! Even these expensive
multipliers from Analog Devices need trimmers.


> I build a frequency doubler some five years ago like that and it worked 
fine.

Without trimming? I bet you had very bad carrier suppression then.
Which might be no problem for a frequency doubler, but is crucial
in a frequency shifter.

JH.