AD831 Analog Devices, AD831 Datasheet - Page 10

• Manufacturer Part Number: AD831
• Description: High-Performance, Low Distortion 500-MHz Mixer
• Manufacturer: Analog Devices

AD831
APPLICATIONS
Careful component selection, circuit layout, power supply
decoupling, and shielding are needed to minimize the AD831’s
susceptibility to interference from radio and TV stations, etc. In
bench evaluation, we recommend placing all of the components
in a shielded box and using feedthrough decoupling networks
for the supply voltage.
Circuit layout and construction are also critical, since stray ca-
pacitances and lead inductances can form resonant circuits and
are a potential source of circuit peaking, oscillation, or both.
Dual-Supply Operation
Figure 25 shows the connections for dual supply operation.
Supplies may be as low as 4.5 V but should be no higher than
5.5 V due to power dissipation.
INPUT
RF
Figure 25. Connections for 5 V Dual-Supply Operation Showing Impedance
Matching Network and Gain of 2 for Driving Reverse-Terminated IF Filter
C1
L1
C2
0.1µF
0.1µF
–5V
–5V
+5V
4
5
6
7
8
0.1µF
GND
RFP
RFN
VN
VN
VP
3
9
AN
50
LO INPUT
–10 dBm
LON
10
2
IFN
82pF
51.1
C
F
–10–
+5V
LOP
11
1
82pF
VP
Top View
C
0.1µF
AD831
The RF input to the AD831 is shown connected by an imped-
ance matching network for an assumed source impedance of
50 . Figure 15 shows the input impedance of the AD831 plot-
ted vs. frequency. The input circuit can be modeled as a resis-
tance in parallel with a capacitance. The 82 pF capacitors (C
connected from IFN and IFP to VP provide a low-pass filter
with a cutoff frequency of approximately 140 MHz in down-
conversion applications (see the Theory of Operation section of
this data sheet for more details). The LO input is connected
single-ended because the limiting amplifier provides a symmet-
ric drive to the mixer. To minimize intermodulation distortion,
connect pins OUT and VFB by the shortest possible path. The
connections shown are for unity-gain operation.
At LO frequencies less than 100 MHz, the AD831’s LO power
may be as low as –20 dBm for satisfactory operation. Above
100 MHz, the specified LO power of –10 dBm must be used.
F
+5V
VP
12
20
0.1µF
IFP
50
GND
19
13
AP
BIAS
COM
VFB
OUT
VN
18
17
16
15
14
51.1
110
NC
0.1µF
R
T
–5V
BPF
R
T
IF
OUTPUT
REV. B
F
)