Current multiplier

Current multiplier based on the Wilson current mirror (2x multiplication)

When we don't only want to copy a current but want to multiply the current by 2 or more, we simply add an extra transistor to the current mirror, so the reference current is copied twice. Because the extra transistor is connected in parallel to the existing transistor, the currents are summed.

In the figures below, a Wilson current mirror is used to multiply the reference current : Iref, by a factor 2.

Current multiplier based on the Wilson current mirror (1.5x multiplication)

Also, non-integer multiplication factors are possible.
In the figure below, a standard current source is used to multiply the reference current : Iref, by a factor 1.5.

Current multiplier based on the Widlar current mirror

Another way to divide or multiply the output current is using the Widlar current mirror, as shown in the figures below :

OPAMP based current multipliers

The circuits above are current mirrors based on an OPAMP instead of bipolar transistors,
In both left circuits, the OPAMP is configured as a voltage buffer. The voltage at the output of the OPAMP will follow the voltage on the non-inverting input.
So we can state that Iref × R1 = [current through R2] × R2.
We also know that : Iout = Iref + [current through R2]. So when combining both formulas, we find that Iout = Iref + (Iref × R1) / R2 = Iref × (1 + R1/R2).
So when R1 = R2, then Iout = 2 × Iref.

In both right circuits, the OPAMP is configured differently to create a current mirror.
Because with an ideal OPAMP, the current flowing into the non-inverting and inverting inputs is 0, we can state that Iref flows through R1 and Iout flows through R2.
The voltage at the output of the OPAMP will be Iref × R1 = Iout × R2.
This results in Iout = (Iref × R1) / R2.
So when R1 = R2, then Iout = Iref.