AD834JRZ-R7 datasheet(13/20 Pages) AD

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Data Sheet

AD834

Rev. F | Page 13 of 20

X1 +VS W1

Y1 Y2 –VS W2

AD834

X-INPUT

±1V FS

Y-INPUT

±1V FS

TERMINATION

RESISTOR

TERMINATION

RESISTOR

+5V

RW RW

1.5RW

4.7Ω

–5V

1µF

CERAMIC

1µF

CERAMIC

COUTPUT

BALUN

SEE

TEXT

Figure 17. Using a Balun at the Output

Note that the upper bandwidth limit of the balun is determined

only by the quality of the transmission line; therefore, the upper

bandwidth of the balun usually exceeds that of the multiplier.

This is unlike a conventional transformer where the signal is

conveyed as a flux in a magnetic core and is limited by core

losses and leakage inductance. The lower limit on bandwidth is

determined by the series inductance of the line, taken as a

whole, and the load resistance (if the blocking capacitors, C, are

sufficiently large). In practice, a balun can provide excellent

differential-to-single-sided conversion over much wider

bandwidths than a transformer.

WIDEBAND MULTIPLIER CONNECTIONS

When operation down to dc and a ground based output are

necessary, the configuration shown in Figure 18 can be used.

The element values were chosen in this example to result in a

full-scale output of ±1 V at the load, so the overall multiplier

transfer function is

W = (X1 − X2)(Y1 − Y2)

where the X1, X2, Y1, Y2 inputs and W output are in volts. The

polarity of the output can be reversed simply by reversing either

the X or Y input.

X1 +VS W1

Y1 Y2 –VS W2

AD834

49.9Ω

0.1µF

+5V

4.7Ω

–5V

49.9Ω

±1V

3.01kΩ

49.9Ω

167Ω

0.01µF

3.01kΩ

261Ω

3.74kΩ

1µF

2.7Ω

90.9Ω

LOAD

49.9Ω

OP AMP

Figure 18. Sideband DC-Coupled Multiplier

Choose the op amp to support the desired output bandwidth.

The op amp originally used in Figure 18 was the AD5539,

providing an overall system bandwidth of 100 MHz. The

AD8009 should provide similar performance. Many other

choices are possible where lower post multiplication band-

widths are acceptable. The level shifting network places the

input nodes of the op amp to within a few hundred millivolts of

ground using the recommended balanced supplies. The output

offset can be nulled by including a 100 Ω trim pot between each

of the lower pair of resistors (3.74 kΩ) and the negative supply.

The pulse response for this circuit is shown in Figure 19; the

X input is a pulse of 0 V to 1 V and the Y input is 1 V dc. The

transition times at the output are about 4 ns.

100

10ns

200mV

Figure 19. Pulse Response for the Circuit of Figure 18

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