AD633 Multiplier IC

AD633 Multiplier IC

The IC AD633 is a multiplier IC by analog devices. It is low cost, 8 pin, 4 quadrant multiplier IC.

The various features of AD633 are,

1. It is complete four quadrant multiplier.

2. No external components or expensive user calibration is necessary.

3. It is low cost and easy to use.

4. It is highly stable and reliable because of monolithic construction and laser calibration.

5. It has differential high impedance X and Y inputs. The input impedance is as high as 10 MΩ.

6. The internal reference is generated by very stable zener diode hence accuracy is not supply sensitive. The scaling reference is 10 V.

7. The total accuracy is 2 % of full scale.

8. It has 1 MHz bandwidth, 20 V/gsec of slew rate and ability to drive capacitive loads.

9. The Z input provides access to the output buffer amplifier, enabling the user to sum the outputs of two or more multipliers, increase the multiplier gain, convert the output voltage to current and configure variety of application circuits.

1. Functional Block Diagram

The Fig. 4.10.1 shows the functional block diagram of AD633.

There are two differential inputs X and Y where X = X₁ - X₂ while Y = Y₁-Y₂. These inputs are converted to the currents by voltage to current converters. The product of these currents is than generated. A buried zener reference generates on overall scale factor of 10 V. Thus the product X + Y / 10 is applied as one input to the summer while Z is another input to the summer. The signal (X+Y / 10 +Z)  is applied to the output amplifier to produce output W. The amplifier summing node Z allows the user to add two or more multiplier outputs, convert the output voltage to current and configure various analog computational functions.

The overall transfer function is,

The Fig. 4.10.2 shows the pin diagram of AD633 multiplier IC. ± VS are the supply pins.

The various applications of AD633 include multiplication, division, squaring, modulation, demodulation, phase detection, attenuators, filters, voltage controlled amplifier etc.

2. Application Circuits

1. Squaring circuit

The Fig. 4.10.3 shows use of AD633 as a squaring circuit

The output polarity can be reversed by interchanging the X and Y inputs.

2. Frequency doubler circuit

For frequency doubling without d.c. term, RC network is used at the input as shown in the Fig. 4.10.4.

At ω, the X input leads the input voltage by 45° and is attenuated by 1/ √2. TheY input lags the X input by 45° and also attenuated by 1/ √2. Thus the X and Y inputs are 90° out of phase. When E is sine wave as E sin ω t then, 

The resistors R₁ and R₂ are included to restore the output amplitude to 10 V for an input amplitude of 10 V.

3. Variable scale factor

For getting a scale factor other than 10, the circuit shown in the Fig. 4.10.5 can be used.

The potential divider at the output increases the scale factor by R₁ + R₂ / R₁. Practically it can be limited upto 100. The summing input S can be used to add additional signal or otherwise it can be grounded.

Review Questions

1. Write a detailed note on AD633 multiplier.

2. Explain any two applications of AD633 multiplier.