Hi,

I don't have any background in electronics, but require to use an existing IC in the form of a Gilbert Multiplier. I came across the circuit on https://www.falstad.com/circuit/ (under transistors), and it's not clear to me what the output voltage is. It seems to be fluctuating likely because of the AC sources, and I don't see it as a product of the two input voltages. Can someone explain the basics of what kind of inputs the circuit takes, and how do we interpret the output. I want to see basic multiplication happening with voltages, like 3 x 2 = 6.

Thanks.

 

I don't have any background in electronics, but require to use an existing IC in the form of a Gilbert Multiplier

I can only speak in generalities . I do not know what IC in particular you are using so I hope this helps you.

From a mathematical point of view, multiplication is a "four quadrant" operation—that is to say
that both inputs may be either positive or negative, as may be the output. Some of the circuits
used to produce electronic multipliers, however, are limited to signals of one polarity. If both
signals must be unipolar, we have a "single quadrant" multiplier, and the output will also be
unipolar. If one of the signals is unipolar, but the other may have either polarity, the multiplier is
a "two quadrant" multiplier, and the output may have either polarity (and is "bipolar"). The
circuitry used to produce one- and two-quadrant multipliers may be simpler than that required for
four quadrant multipliers, and since there are many applications where full four quadrant
multiplication is not required, it is common to find accurate devices which work only in one or
two quadrants.

 

There is an Analog Multiplier Tutorial by Analog Devices that should give you some insight into the Gilbert Cell and its variants. Rather than try to make your own, I'd suggest using a packaged analog multiplier chip such as the AD633. Analog Devices has others as well, with various functionality.

 

Memorize the formula at the bottom of figure 4. It tells us a lot about how bipolar transistors work.

Barrie Gilbert (5 June 1937 – 30 January 2020) was an English-American inventor. He was well known for his invention of numerous analog circuit concepts, holding over 100 patents worldwide, and for the discovery of the Translinear Principle.

 

Barrie Gilbert (5 June 1937 – 30 January 2020) was an English-American inventor. He was well known for his invention of numerous analog circuit concepts, holding over 100 patents worldwide, and for the discovery of the Translinear Principle.

Didn't know that he had passed away. Became familiar with his gain cell back in the 70's.