PWL Multipliers

Piecewise Linear (PWL) Multiplication provides a simple way to multiply multiple time-varying signals with high bandwidth. The PWL multiplication method exploits the fact that the multiplication of two time-varying signals, VA and VB can be represented in a log-anti-log format: VA×VB=10(log(VA)+log(VB)) The resulting output has error due to the PWL implementation of the log and anti-log functions.

Advantages:

  • Infinite bandwidth. A very fast moving signal applied to the input will appear at the output without delay.
  • Compatible with the POP and AC analyses

Disadvantages:

  • Poor accuracy around portions of the input range. This inaccuracy is due to the fact that the log and exponential portions of the multiplier are PWL and not continuous.

PWL Multiplication Example

You can download this example here: 1.9_SIMPLIS_Multiplication.sxsch

This example uses PWL resistors to create the log(VA) and $log\left( V_B \right)$ signals, these signals are then added with a Summer and a final anti-log PWL resistor is used to generate the output voltage.

This example circuit also has a PWM Multiplier example and the error of each technique is plotted on the output graph.