Datasheet

LTC6430-15
13
643015f
applicaTions inForMaTion
Balanced Amplifier Circuit, 50Ω Input and 50Ω Output
This balanced amplifier circuit is a replica of the Test
Circuit A. It is useful for single-ended 50Ω amplifier require-
ments and is surprisingly wideband. Using this balanced
arrangement and the frequency appropriate baluns, one
can achieve the intermodulation and harmonic performance
listed in the AC Electrical Characteristics specifications
of this data sheet. Besides its impressive intermodula-
tion performance, the LTC6430-15 has impressive 2nd
harmonic suppression as well. This makes it particularly
well suited for multioctave applications where the 2nd
harmonic cannot be filtered.
This balanced circuit example uses two Mini-Circuits 1:2
baluns. The baluns were chosen for their bandwidth and
frequency options that utilize the same package footprint
(see Table 2). A pair of these baluns, back-to-back has
less than 1.5dB of loss, so the penalty for this level of
performance is minimal. Any suitable 1:2 balun may be
used to create a balanced amplifier with the LTC6430-15.
The optional stability network is only required when the
balun’s bandwidth reaches below 20MHz. It is included in
the circuit as a comprehensive protection for any passive
element placed at the LTC6430-15 input. Its performance
degradation at low frequencies can
be mitigated by increas-
ing the 60pF capacitor’s value.
Demo
Boards 1774A-A and 1774A-B implement this
balanced amplifier circuit. It is shown in Figure 18 and
Figure 19.
Please note that a number of DNC pins are connected on
the evaluation board. These connections are not necessary
for normal circuit operation.
The evaluation board also includes an optional back to
back pair of baluns so that their losses may be measured.
This allows the designer to de-embed the balun losses and
more accurately predict the LTC6430-15 performance in
a differential circuit.
Table 2. Target Frequency and Suggested 2:1 Balun
FREQUENCY BAND (MHz) MODEL NUMBER MANUFACTURER
50 to 300 ADT2-1T Mini-Circuits
www.minicircuits.com
300 to 400 ADT2-1P
400 to 1300 ADTL2-18
Figure 2. Balanced Amplifier Circuit, 50Ω Input and 50Ω Output
643015 F02
V
CC
= 5V
T1
1:2
PORT
INPUT
RF
OUT
50Ω, SMA
RF
IN
50Ω, SMA
PORT
OUTPUT
BALUN_A
BALUN_A
BALUN_A = ADT2-1T FOR 50MHz TO 300MHz
BALUN_A = ADT2-1P FOR 300MHz TO 400MHz
BALUN_A = ADTL2-18 FOR 400MHz TO 1300MHz
ALL ARE MINI-CIRCUITS CD542 FOOTPRINT
C1
1000pF
L1
560nH
LTC6430-15
DNC
DNC
DNC
DNC
DNC
DNC
+OUT
GND
T_DIODE
DNC
GND
–OUT
+IN
GND
V
CC
DNC DNC DNC
–IN GND V
CC
DNC DNC DNC
••
C2
1000pF
C4
1000pF
C3
1000pF
C7
60pF
C5
1000pF
R1
350Ω
C6
0.1µF
C8
60pF
OPTIONAL STABILITY
NETWORK
R2
350Ω
100Ω
DIFFERENTIAL
100Ω
DIFFERENTIAL
L2
560nH
T2
2:1