Datasheet

AD539
Rev. B | Page 16 of 20
BASIC DIVIDER CONNECTIONS
Standard Scaling
The AD539 provides excellent operation as a two-quadrant
analog divider in wideband, wide gain-range applications, with
the advantage of dual-channel operation. Figure 25 shows the
simplest connections for division with a transfer function of
V
Y
= −V
U
V
W
/V
X
Recalling that the nominal value of V
U
is 1 V, this can be
simplified to
V
Y
= −V
W
/V
X
where all signals are expressed in volts. The circuit thus exhibits
unity gain for V
X
= 1 V and a gain of 40 dB when V
X
= 0.01 V.
The output swing is limited to ±2 V nominal full scale and ±4.2 V
peak (using a −V
S
supply of at least 7.5 V for the AD539).
Because the maximum loss is 10 dB (at V
X
= 3.162 V), it follows
that the maximum input to V
W
should be ±6.3 V (4.4 V rms) for
low distortion applications and no more than ±13.4 V (9.5 V
rms) to avoid clipping. Note that offset adjustment is needed for
the op amps to maintain accurate dc levels at the output in high
gain applications: the noise gain is 6 V/V
X
, or 600 at V
X
= 0.01 V.
The gain magnitude response for this configuration using the
LH0032 op amps with nominally 12 pF compensation (HF
COMP, Pin 2, to V
Y1
, Pin 3) and C
F
= 7 pF is shown in Figure 17;
however, other amplifiers can also be used. Because there is some
manufacturing variation in the HF response of the op amps and
load conditions also affect the response, these capacitors should
be adjustable: 5 pF to 15 pF is recommended for both positions.
The bandwidth in this configuration is nominally 17 MHz at
V
X
= 3.162 V, 4.5 MHz at V
X
= 1 V, 350 kHz at V
X
= 0.1 V, and
35 kHz at V
X
= 0.01 V. The general recommendations regarding
the use of a good ground plane and power supply decoupling
should be carefully observed. Other suitable high speed op amps
include: AD844, AD827, and AD811. Consult these data sheets
for suitable applications circuits.
09679-025
1
2
3
4
16
15
14
13
5 12
6 11
7 10
8 9
AD539
V
X
NUMERATOR 1
V
W1
NUMERATOR 2
V
W2
HF COMP
V
Y1
+V
S
–V
S
V
Y2
INPUT
COMMON
OUTPUT
COMMON
BASE
COMMON
W1
Z1 NC
3
3
2
2pF TO 15pF
LH0032
2pF TO
15pF
2pF TO
15pF
NOTES
1. DECOUPLE OP AMP SUPPLIES.
2pF TO 15pF
2
NC
CHAN1
OUTPUT
CHAN2
OUTPUT
Z2
W2
C
C
= 3nF
DENOMINATOR
INPUT, V
X
V
Y1
= –
V
W1
V
X
V
Y2
= –
V
W2
V
X
0.47µF
0.47µF
+5V
–7.5V
Figure 25. 2-Channel Divider with 1 V Scaling (16-Lead SBDIP and PDIP Shown)