Re: analog multiplier help

Hello Adam ,
What exact part number do you need?
I will get you a price.
Thanks Mike
mike@xxxxxxxx


Adam S wrote:
> I'm looking for an "mixer" circuit to detect a sine waves DC to 10MHz,
> 3Vp-p max, and use IF output of 5kHz. Both the LO and the signal inputs
> are generated by DDSs. If large harmonics are present on the LO then
> there is good possibility they will mix with non-harmonic spurs
> generated by the signal DDS. RF mixers are generally square wave LO
> driven (or sine waves that fully switch long tail pair transistors) and
> therefore will generate lots of harmonics. This is the reason an analog
> multiplier is in my mind. LO 3rd harmonic of -40dB is low enough.
>
> Currently manufactured multiplier ICs I have found:
>
> AD835 (expensive, easy to use)
> AD633 (cost ok, but only 1MHz)
> HA2556 (price ?, difficult to buy)
>
> I looked at a discrete design with total of 19 NPN transistors + 1
> op-amp. (see schematic
> http://members.optusnet.com.au/~eseychell/pictures/0001.png )
>
> SPice simulation of perfectly matched transistors gives great
> results on screen, but I'm very unsure what will happen in practice.
> Voltage offsets at each input will cause carrier feedthrough, but these
> can be trimmed out with yet more components. Neither power consumption
> or supply voltages are a concern.
>
> Apart from the high part count is there any major problems with going
> for a discrete analog multiplier ?

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