Analog Multiplier vs. Digital Multiplier: Key Differences

This article compares analog multipliers and digital multipliers, highlighting the key differences between the two.

Analog Multiplier

Definition: An analog multiplier is a device with two input ports and one output port. The output signal is the product of the two input signals. This is visualized in Figure 1.

Figure 1: Analog Multiplier

As shown in the figure, the output voltage (Vout) is equal to Vx * Vy / K, where K is the scale factor. The polarity of the output (Vout) depends on the polarity of the two input signals (positive or negative). The relationship is shown in Table 1. Based on these input/output combinations, there are various “quadrant types” for analog multipliers.

Table 1: Analog Multiplier Quadrant Types

Digital Multiplier

The common method of digital multiplication is the “add and shift algorithm.” Following are the basic types of digital multipliers:

• Serial or parallel multiplier
• Shift and Add multiplier
• Array multiplier
• Booth multiplier
• Modified Booth multiplier
• Wallace Tree multiplier
• Combined booth and Wallace tree multiplier

Figure 2: 4-bit Digital Multiplier

Figure 2 depicts an array multiplier based on the add/shift algorithm. Each partial product is the result of the multiplication of the multiplicand and a multiplier bit. Partial products are shifted according to their respective bit orders and then added. The addition operation typically uses a normal carry propagate method. For a multiplier of length N, a total of N-1 adders are needed.

Figure 3: 4-bit Digital Multiplier Circuit

Figure 3 depicts a 4-bit digital multiplier circuit.