AD844_15 Datasheet, PDF (18/20 Pages) Analog Devices – 60 MHz 2000 V/s Monolithic Op Amp

AD844
Figure 45 shows the small signal response for a 50 dB gain control
range (VX = 10 mV to 3.16 V). At small values of VX, capacitive
feedthrough on the PC board becomes troublesome and very
careful layout techniques are needed to minimize this problem.
A ground strip between the pins of the AD539 is helpful in this
regard. Figure 46 shows the response to a 2 V pulse on VY for
VX = 1 V, 2 V, and 3 V. For these results, a load resistor of 500 Ω
was used and the supplies were ±9 V. The multiplier operates
from supplies between ±4.5 V and ±16.5 V.
Disconnecting Pin 9 and Pin 16 on the AD539 alters the
denominator in Equation 1 to 1 V, and the bandwidth is
approximately 10 MHz, with a maximum gain of 10 dB.
Using only Pin 9 or Pin 16 results in a denominator of 0.5 V,
a bandwidth of 5 MHz, and a maximum gain of 16 dB.
4
V_X = 3.15V
–6
V_X = 1.0V
–16
V_X = 0.316V
–26
V_X = 0.10V
–36
V_X = 0.032V
–46
–56
100k
1M
10M
60M
FREQUENCY (Hz)
Figure 45. VGA AC Response
1V 1V
100
90
50ns
10
0
Figure 46. VGA Transient Response with VX = 1 V, 2 V, and 3 V
Rev. F | Page 18 of 20