With this circuit, you can generate an output proportional to the absolute
value of the difference between two input voltages, V1 and V2 (see
the figure).
The circuit handles input signals over the voltage range of 0 to +5 V, and
operates from a single 5-V power supply. Its output voltage is equal to 4.994
× |V − V2|.
The circuit uses three-fourths of an LM660, as an inverting stage (the leftmost
U1), a rectifier (the middle U1), and an output stage to provide gain and level
shifting.
The approximate output current is Io = | V1 − V2 |/R1;
the approximate output voltage is calculated from Vo= 2.5 (1 –
RF/RB) + (Io × RF).
