AD734

–10–

REV. C

SQUARE WAVE

SINE WAVE

TRI-WAVE

10k

100k

1M

10M

INPUT FREQUENCY – Hz

100

10

1

100m

10m

1m

100

Figure 16. RMS-DC Converter Performance

LOW DISTORTION MIXER

The AD734’s low noise and distortion make it especially

suitable for use as a mixer, modulator, or demodulator.

Although the AD734’s –3 dB bandwidth is typically 10 MHz

and is established by the output amplifier, the bandwidth of its

X and Y interfaces and the multiplier core are typically in excess

of 40 MHz. Thus, provided that the desired output signal is less

than 10 MHz, as would typically be the case in demodulation,

the AD734 can be used with both its X and Y input signals as

high as 40 MHz. One test of mixer performance is to linearly

combine two closely spaced, equal-amplitude sinusoidal signals

and then mix them with a third signal to determine the mixer’s

2-tone Third-Order Intermodulation Products.

1

2

3

4

5

6

7

10

8

9

11

13

12

14

W

ER

VN

VP

DD

Z1

Z2

X1

X2

U1

U2

U0

Y1

Y2

AD734

0.1 F

0.1 F

+15V

–15V

2k

HP3326A

COMBINE

A + B

DATEL

DVC-8500

HP3326A

HIGH VOLTAGE

OPTION

HP3585A

WITH 10X PROBE

dBm REF TO 50

AD707

Figure 17. AD734 Mixer Test Circuit

Figure 17 shows a test circuit for measuring the AD734’s perfor-

mance in this regard. In this test, two signals, at 10.05 MHz and

9.95 MHz are summed and applied to the AD734’s X interface.

A second 9 MHz signal is applied to the AD734’s Y interface.

The voltage at the U interface is set to 2 V to use the full

dynamic range of the AD734. That is, by connecting the W and

Z1 pins together, grounding the Y2 and X2 pins, and setting

U = 2 V, the overall transfer function is

W

=

X

2 V

(14)

and W can be as high as 20 V p-p when X1 = 2 V p-p and Y1 =

10 V p-p. The 2 V p-p signal level corresponds to +10 dBm into

a 50

Ω input termination resistor connected from X1 or Y1 to

ground.

±

± f

in Figure 19. This performance is without external trimming of

the AD734’s X and Y input-offset voltages.

The possible Two Tone Intermodulation Products are at 2

×

9.95 MHz – 10.05 MHz

± 9.00 MHz and 2 × 10.05 –

9.95 MHz

± 9.00 MHz; of these only the third-order products

at 0.850 MHz and 1.150 MHz are within the 10 MHz band-

width of the AD734; the desired output signals are at

0.950 MHz and 1.050 MHz. Note that the difference (Figure

18) between the desired outputs and third-order products is

approximately 78 dB, which corresponds to a computed

third-order intercept point of +46 dBm.

Figure 18. AD734 Third-Order Intermodulation Performance

played Signal Levels Are Attenuated 20 dB by the 10X Probe

Used to Measure the Mixer’s Output

Figure 19. AD734 Third-Order Intermodulation Performance

played Signal Levels Are Attenuated 20 dB by the 10X Probe

Used to Measure the Mixer’s Output