AD605

Rev. E | Page 17 of 20

Figure 40 shows the gain vs. VGN for the circuit in Figure 39 at

1 MHz and the lowest gain range (−14 dB to +34.4 dB). Note

that the gain scaling is 40 dB/V, double the 20 dB/V of an

individual DSX; this is the result of the parallel connection of

the gain control inputs, VGN1 and VGN2. One could, of

course, also sequentially increase the gain by first increasing the

gain of Channel 1 and then Channel 2. In this case, VGN1 and

VGN2 are driven from separate voltage sources, for instance

two separate DACs. Figure 41 shows the gain error of Figure 39.

80

–40

f = 1MHz

ACTUAL

0

70

20

–10

–20

–30

50

30

60

40

10

VGN (V)

THEORETICAL

0.1

0.5

0.9

1.3

1.7

2.1

2.5

2.9

Figure 40. Gain vs. VGN for the Circuit in Figure 39

VGN (V)

4

3

–4

0

–1

–2

–3

2

1

f = 1MHz

0.2

0.7

1.2

1.7

2.2

2.7

Figure 41. Gain Error vs. VGN for the Circuit in Figure 39