08-06-2013, 01:54 PM
ANALOG MULTIPLIER
[attachment=55007]
INTRODUCTION
An analog multiplier is a device having two input ports and an output port. The signal at the output is the product of the two input signals. If both input and output signals are voltages, the transfer characteristic is the product of the two voltages divided by a scaling factor, K, which has the dimension of voltage as shown in Figure 1.
From a mathematical point of view, multiplication is a "four quadrant" operation—that is to say that both inputs may be either positive or negative, as may be the output. Some of the circuits used to produce electronic multipliers, however, are limited to signals of one polarity. If both signals must be unipolar, we have a "single quadrant" multiplier, and the output will also be unipolar. If one of the signals is unipolar, but the other may have either polarity, the multiplier is a "two quadrant" multiplier, and the output may have either polarity (and is "bipolar"). The circuitry used to produce one- and two-quadrant multipliers may be simpler than that required for four quadrant multipliers, and since there are many applications where full four quadrant multiplication is not required, it is common to find accurate devices which work only in one or two quadrants. An example is the AD539, a wideband dual two-quadrant multiplier which has a single unipolar Vy input with a relatively limited bandwidth of 5 MHz, and two bipolar Vx inputs, one per multiplier, with bandwidths of 60 MHz. A block diagram of the AD539 is shown in Figure 2.
[attachment=55007]
INTRODUCTION
An analog multiplier is a device having two input ports and an output port. The signal at the output is the product of the two input signals. If both input and output signals are voltages, the transfer characteristic is the product of the two voltages divided by a scaling factor, K, which has the dimension of voltage as shown in Figure 1.
From a mathematical point of view, multiplication is a "four quadrant" operation—that is to say that both inputs may be either positive or negative, as may be the output. Some of the circuits used to produce electronic multipliers, however, are limited to signals of one polarity. If both signals must be unipolar, we have a "single quadrant" multiplier, and the output will also be unipolar. If one of the signals is unipolar, but the other may have either polarity, the multiplier is a "two quadrant" multiplier, and the output may have either polarity (and is "bipolar"). The circuitry used to produce one- and two-quadrant multipliers may be simpler than that required for four quadrant multipliers, and since there are many applications where full four quadrant multiplication is not required, it is common to find accurate devices which work only in one or two quadrants. An example is the AD539, a wideband dual two-quadrant multiplier which has a single unipolar Vy input with a relatively limited bandwidth of 5 MHz, and two bipolar Vx inputs, one per multiplier, with bandwidths of 60 MHz. A block diagram of the AD539 is shown in Figure 2.