–10–

REV. B

APPLICATIONS

The MLT04 is well suited for such applications as modulation/

demodulation, automatic gain control, power measurement, analog

computation, voltage-controlled amplifiers, frequency doublers,

and geometry correction in CRT displays.

Multiplier Connections

Figure 43 llustrates the basic connections for multiplication. Each

of the four independent multipliers has single-ended voltage inputs

(X, Y) and a low impedance voltage output (W). Also, each

multiplier has its own dedicated ground connection (GND) which

is connected to the circuit’s analog common. For best perfor-

mance, circuit layout should be compact with short component

leads and well-bypassed supply voltage feeds. In applications where

fewer than four multipliers are used, all unused analog inputs must

be returned to the analog common.

Figure 43. Basic Multiplier Connections

Squaring and Frequency Doubling

As shown in Figure 44, squaring of an input signal, V

by connecting the X-and Y-inputs in parallel to produce an output

of V

IN

will be positive.

Figure 44. Connections for Squaring

When the input is a sine wave given by V

circuit behaves as a frequency doubler because of the trigonometric

identity:

(V

IN

sin

2.5V

=

V

IN

2

2.5V

1

2









(1

− cos 2ωt )

The equation shows a dc term at the output which will vary

strongly with the amplitude of the input, V

The output dc offset

can be eliminated by capacitively coupling the MLT04’s output

with a high-pass filter. For optimal spectral performance, the

filter’s cutoff frequency should be chosen to eliminate the input

fundamental frequency.

A source of error in this configuration is the offset voltages of the X

and Y inputs. The input offset voltages produce cross products

with the input signal to distort the output waveform. To circum-

vent this problem, Figure 45 illustrates the use of inverting

amplifiers configured with an OP285 to provide a means by which

the X- and Y-input offsets can be trimmed.

Figure 45. Frequency Doubler with Input Offset Voltage

Trims

Feedback Divider Connections

The most commonly used analog divider circuit is the “inverted

multiplier” configuration. As illustrated in Figure 46, an “inverted

multiplier” analog divider can be configured with a multiplier

operating in the feedback loop of an operational amplifier. The

general form of the transfer function for this circuit configuration is

given by:

V

O

=−2.5V ×

R2

R1









×

V

IN

V

X

Here, the multiplier operates as a voltage-controlled potentiometer

that adjusts the loop gain of the op amp relative to a control signal,

V

As the control signal to the multiplier decreases, the output of

the multiplier decreases as well. This has the effect of reducing

negative feedback which, in turn, decreases the amplifier’s loop

gain. The result is higher closed-loop gain and reduced circuit

bandwidth. As V

increases which generates more negative feedback — closed-loop

gain drops and circuit bandwidth increases. An example of an

“inverted multiplier” analog divider frequency response is shown in

Figure 47.

MLT04

1

2

3

4

5

6

7

8

9

18

17

16

15

14

13

12

11

10

18

17

16

15

14

13

12

11

10

4

1

2

3

5

6

7

8

9

MLT04

W4

GND4

X4

V

EE

Y4

Y3

X3

GND3

W3

W1

GND1

X1

Y1

V

CC

Y2

X2

GND2

W2

W4

X4

Y4

Y3

X3

W3

0.1µF

–5V

0.1µF

W1

X1

Y1

Y2

X2

W2

+5V

0.4

+5V

–5V

X

GND

Y

W

1/4 MLT04

V

IN

0.1µF

0.1µF

W = 0.4 V

IN

2

+

+

L

10k

Ω

C1

100pF

1/4 MLT04

0.4

3

2

1

W1

4

+

+

2

3

1

A1

A1, A2 = 1/2 OP285

+

R2

10k

500k

Ω

50k

Ω

R1

10k

+5V

–5V

6

5

7

A2

+

R4

10k

500k

Ω

50k

Ω

R3

10k

+5V

–5V