current mode analog multiplier design

[ramraj_gp]

Does anyone know about how to design "current mode" analog multiplier. I mean I0=I1*I2

 

[aryajur]

You can do this using BJTs easily. If you put each current (I1 and I2)through a diode connected BJT and then form a high resistance voltage divider between their collectors/bases and then tap the resistor divider and feed it to the base of another BJT, the current in the 3rd BJT will be proportional to the product of I1 and I2.

Vbe1 = Vt ln(I1/Is)
Vbe2 = Vt ln(I2/Is)
Voltage at tap = (Vbe1 + Vbe2)/2 = Vt ln(I1.I2/Is²)

if this is the Vbe of the 3rd transistor then current through it will be:

Ie3 = Io = Is exp(Vt ln(I1.I2/Is²) / Vt) = I1. I2 / Is

If you want I will upload a schematic.

 

[xmli1976]

please upload the schematic.thanks

 

[pandpap]

This paper might help...
This is a CMOS implementation...

 

[aryajur]

Here is the schematic

 

[crystal]

Search for current mode blocks like current conveyor and gilbert cell. Should give you a better idea on what's current mode as well as multiplier.