HITTITE HMC708LP5_10

HMC708LP5 / 708LP5E
v03.0409
0.5 dB LSB 6-BIT DIGITAL
VARIABLE GAIN AMPLIFIER, 1700 - 2200 MHz
Typical Applications
Features
The HMC708LP5(E) is ideal for:
-2.5 to +29 dB Gain Control in 0.5 dB Steps
• Cellular Infrastructure
Power-up State Selection
• WiBro, WiMAX and LTE/ 4G
High Output IP3: +37 dBm
• Microwave Radio & VSAT
Low Noise Figure: 1 dB
• Test Equipment and Sensors
TTL/CMOS Compatible
Serial, Parallel, or Latched Parallel Control
±0.25 dB Typical Step Error
Single +3V and +5V Supply
32 Lead 5x5mm SMT Package: 25mm2
Functional Diagram
General Description
Variable gain amplifiers - digital - SMT
12
12 - 1
The HMC708LP5(E) is a digitally controlled variable
gain amplifier which operates from 1700 MHz and
2200 GHz, and can be programmed to provide
between 2.5 dB attenuation and +29 dB of gain, in
0.5 dB steps. The HMC708LP5(E) delivers noise
figure of 1 dB in its maximum gain state, with output
IP3 of up to +37 dBm. The dual mode gain control
interface accepts either three wire serial input or
6 bit parallel word. The HMC708LP5(E) also features
a user selectable power up state and a serial
output for cascading other Hittite serially controlled
components. For 900 MHz applications please refer
to the HMC707LP5(E) data sheet.
Electrical Specifications, TA = +25° C
Rbias = 270 Ohms for Vdd = +5V, Rbias = 10 kOhms for Vdd = +3V, Vdd = Vdd1 = Vdd2 = Vdd3
Min.
Parameter
Typ.
Max.
Min.
Vdd = +3V
Frequency Range
23
Max.
Vdd = +5V
1.7 - 2.2
Gain (Maximum Gain State)
Typ.
1.7 - 2.2
27
25
Units
GHz
30
dB
Gain Control Range
31.5
31.5
dB
Input Return Loss
16.5
20.5
dB
Output Return Loss
10.5
13.5
dB
±(0.3 + 8%) of Attenuation Setting
±(0.2 + 5%) of Attenuation Setting
dB
Attenuation Accuracy: (Referenced to Maximum Gain State)
Output Power for 1 dB Compression
13
Output Third Order Intercept Point
(Two-Tone Input Power= -10 dBm Each Tone)
Noise Figure
Switching Characteristics
tRISE, tFALL (50% CTL to 90% RF)
tRISE
tFALL
16
18
21.5
dBm
32.5
37.5
dBm
1.1
1
dB
-
140
270
ns
ns
Current Amplifier 1
30
47
65
80
97
135
mA
Current Amplifier 2
130
155
190
130
155
190
mA
[1] Two-tone output power @ -10 dBm [2] Two-tone output power @ -5 dBm
For price, delivery and to place orders: Hittite Microwave Corporation, 20 Alpha Road, Chelmsford, MA 01824
Phone: 978-250-3343
Fax: 978-250-3373
Order On-line at www.hittite.com
Application Support: Phone: 978-250-3343 or [email protected]
HMC708LP5 / 708LP5E
v03.0409
0.5 dB LSB 6-BIT DIGITAL
VARIABLE GAIN AMPLIFIER, 1700 - 2200 MHz
Normalized Attenuation
Maximum Gain vs. Frequency [1]
(Only Major States are Shown)
40
+25C
+85C
-40C
GAIN (dB)
36
32
28
24
20
1.5
Vdd=3V
1.7
1.9
2.1
FREQUENCY (GHz)
2.3
-5
-10
-15
-20
Vdd=3V
Vdd=5V
-25
-30
-35
1.5
2.5
1.6
1.7
1.8
1.9
2
2.1 2.2
FREQUENCY (GHz)
Input Return Loss
Output Return Loss
(Only Major States are Shown)
(Only Major States are Shown)
Vdd=3V
Vdd=5V
-10
-20
-30
-40
1.5
2.4
2.5
12
0
RETURN LOSS (dB)
RETURN LOSS (dB)
0
2.3
1.7
1.9
2.1
FREQUENCY (GHz)
2.3
Vdd=3V
Vdd=5V
-5
-10
-15
-20
1.5
2.5
1.7
1.9
2.1
FREQUENCY (GHz)
2.3
2.5
Output IP3 vs. Attenuation @ 1900 MHz
Output IP3 vs. Tone Power [1]
48
40
Pout=-15dBm
Pout=-10dBm
Pout= -5dBm
Pout= 0dBm
44
Power Out = -10dBm
Vdd=5V
30
IP3 (dBm)
IP3 (dBm)
40
36
20
32
Vdd=3V
Vdd=5V
10
28
Vdd=3V
24
1.7
1.8
1.9
2
FREQUENCY (GHz)
2.1
2.2
0
0
4
8
12
16
20
24
ATTENUATION STATE (dB)
28
32
variable gain amplifiers - digital - SMT
NORMALIZED ATTENUATION (dB)
0
Vdd=5V
[1] Maximum gain state with digital attenuator set to minimum attenuation
For price, delivery and to place orders: Hittite Microwave Corporation, 20 Alpha Road, Chelmsford, MA 01824
Phone: 978-250-3343
Fax: 978-250-3373
Order On-line at www.hittite.com
Application Support: Phone: 978-250-3343 or [email protected]
12 - 2
HMC708LP5 / 708LP5E
v03.0409
0.5 dB LSB 6-BIT DIGITAL
VARIABLE GAIN AMPLIFIER, 1700 - 2200 MHz
Bit Error vs. Frequency @ +3V
Bit Error vs. Frequency @ +5V
(Only Major States are Shown)
(Only Major States are Shown)
3
3
2
BIT ERROR (dB)
BIT ERROR (dB)
2
1
0
-1
-1
Vdd = 5V
-2
-3
1.5
1.7
1.9
12
2.1
2.3
-3
1.5
2.5
1.7
1.9
Bit Error vs. Attenuation State @ +3V
2.3
2.5
Bit Error vs. Attenuation State @ +5V
2.5
2.5
Vdd=3V (1.7, 1.8, 1.9, 2.0, 2.1, 2.2) GHz
2
BIT ERROR (dB)
2
1.5
1
0.5
0
-0.5
2.1
FREQUENCY (GHz)
FREQUENCY (GHz)
Vdd=5V (1.7, 1.8, 1.9, 2.0, 2.1, 2.2) GHz
1.5
1
0.5
0
0
4
8
12
16
20
24
ATTENUATION STATE (dB)
28
32
-0.5
0
4
8
12
16
20
24
ATTENUATION STATE (dB)
28
32
Normal Relative Phase vs. Frequency
(Only Major States are Shown)
30
RELATIVE PHASE (deg)
BIT ERROR (dB)
Variable gain amplifiers - digital - SMT
0
Vdd = 3V
-2
12 - 3
1
20
10
0
-10
Vdd=3V
Vdd=5V
-20
-30
1.5
1.7
1.9
2.1
FREQUENCY (GHz)
2.3
2.5
For price, delivery and to place orders: Hittite Microwave Corporation, 20 Alpha Road, Chelmsford, MA 01824
Phone: 978-250-3343
Fax: 978-250-3373
Order On-line at www.hittite.com
Application Support: Phone: 978-250-3343 or [email protected]
HMC708LP5 / 708LP5E
v03.0409
0.5 dB LSB 6-BIT DIGITAL
VARIABLE GAIN AMPLIFIER, 1700 - 2200 MHz
Step Error vs. Frequency @ +5V
Step Error vs. Frequency @ +3V
(Only Major States are Shown)
(Only Major States are Shown)
2
2
Vdd = 5V
0
-1
-2
1.5
1.7
1.9
2.1
FREQUENCY (GHz)
2.3
0
-1
-2
1.5
2.5
Noise Figure vs. Frequency
1.7
1.9
2.1
FREQUENCY (GHz)
2.3
2.5
12
Noise Figure vs. Attenuation @ 1900 MHz
2
20
Vdd=3V
Vdd=5V
Vdd=3V
Vdd=5V
16
NOISE FIGURE (dB)
1.6
NOISE FIGURE (dB)
1
1.2
0.8
0.4
12
8
4
0
1.5
1.7
1.9
2.1
FREQUENCY (GHz)
2.3
0
2.5
Output IP3 & Supply Current vs.
Supply Voltage @ 1900 MHz
0
4
8
12
16
20
24
ATTENUATION (dBm)
28
32
Output IP3 & Supply Current vs.
Rbias @ 1900 MHz
300
45
500
40
250
35
400
36
200
32
150
15
100
5
44
IP3 (dBm)
Vdd=3V
Vdd=5V
25
300
200
IP3 @1.9GHz
28
2.7
3.1
3.5
3.9
4.3
4.7
VOLTAGE SUPPLY (V)
5.1
5.5
100
1
10
100
Rbias (Ohms)
1000
10000
For price, delivery and to place orders: Hittite Microwave Corporation, 20 Alpha Road, Chelmsford, MA 01824
Phone: 978-250-3343
Fax: 978-250-3373
Order On-line at www.hittite.com
Application Support: Phone: 978-250-3343 or [email protected]
DC CURRENT (mA)
Idd (mA)
IP3 (dBm)
Idd
variable gain amplifiers - digital - SMT
STEP ERROR (dB)
STEP ERROR (dB)
Vdd = 3V
1
12 - 4
HMC708LP5 / 708LP5E
v03.0409
0.5 dB LSB 6-BIT DIGITAL
VARIABLE GAIN AMPLIFIER, 1700 - 2200 MHz
Option 1 [1] : Amp1 + 6-Bit DAT only
Gain & Return Loss [1] [2]
Noise Figure vs. Frequency [1] [2]
2
30
S21
10
Vdd=3V
Vdd=5V
0
-10
S11
S22
1.6
1.7
1.8
1.9
2
2.1 2.2
FREQUENCY (GHz)
0.8
2.3
2.4
2.5
0
1.5
1.7
1.9
2.1
FREQUENCY (GHz)
2.3
2.5
Output IP3 vs. Attenuation @ 1900 MHz [1]
30
Power Out = -20dBm
20
IP3 (dBm)
Variable gain amplifiers - digital - SMT
12
1.2
0.4
-20
-30
1.5
Vdd=3V
Vdd=5V
1.6
NOISE FIGURE (dB)
RESPONSE (dB)
20
10
Vdd=3V
Vdd=5V
0
-10
-20
0
4
8
12
16
20
24
ATTENUATION STATE (dB)
28
32
[1] See Application Circuit [2] Maximum gain state with digital attenuator set to minimum attenuation
12 - 5
For price, delivery and to place orders: Hittite Microwave Corporation, 20 Alpha Road, Chelmsford, MA 01824
Phone: 978-250-3343
Fax: 978-250-3373
Order On-line at www.hittite.com
Application Support: Phone: 978-250-3343 or [email protected]
HMC708LP5 / 708LP5E
v03.0409
0.5 dB LSB 6-BIT DIGITAL
VARIABLE GAIN AMPLIFIER, 1700 - 2200 MHz
Option 2 [1] : 6-Bit DAT + Amp2 only
Gain & Return Loss [1] [2]
Output IP3 vs. Attenuation @ 1900 MHz [1]
44
20
Pout=0dBm
15
40
S21
Setup limit
36
5
IP3 (dBm)
Vdd=3V
Vdd=5V
0
S11
-5
32
Pout=-5dBm
28
Vdd=3V
Vdd=5V
-10
24
-15
-20
1.5
S22
1.6
1.7
20
1.8
1.9
2
2.1 2.2
FREQUENCY (GHz)
2.3
2.4
2.5
0
4
8
12
16
20
24
ATTENUATION STATE (dB)
28
32
Serial Control Interface
The HMC708LP5(E) contains a 3-wire SPI compatible digital interface (SERIN, CLK, LE). It is activated when P/S
is kept high. The 6-bit serial word must be loaded MSB first. The positive-edge sensitive CLK and LE requires
clean transitions. Standard logic families work well. If mechanical switches were used, sufficient debouncing should
be provided. When LE is high, 6-bit data in the serial input register is transferred to the attenuator. When LE is high
CLK is masked to prevent data transition during output loading.
When P/S is low, 3-wire SPI interface inputs (SERIN, CLK, LE) are disabled and serial input register is loaded
asynchronously with parallel digital inputs (D0-D5). When LE is high, 6-bit parallel data is transferred to the attenuator.
For all modes of operations, attenuation state will stay constant while LE is kept low.
[1] See Application Circuit [2] Maximum gain state with digital attenuator set to minimum attenuation
For price, delivery and to place orders: Hittite Microwave Corporation, 20 Alpha Road, Chelmsford, MA 01824
Phone: 978-250-3343
Fax: 978-250-3373
Order On-line at www.hittite.com
Application Support: Phone: 978-250-3343 or [email protected]
12
variable gain amplifiers - digital - SMT
RESPONSE (dB)
10
12 - 6
HMC708LP5 / 708LP5E
v03.0409
0.5 dB LSB 6-BIT DIGITAL
VARIABLE GAIN AMPLIFIER, 1700 - 2200 MHz
Timing Diagram (Latched Parallel Mode)
Variable gain amplifiers - digital - SMT
12
12 - 7
Parameter
Typ.
Min. serial period, tSCK
100 ns
Control set-up time, tCS
20 ns
Control hold-time, tCH
20 ns
LE setup-time, tLN
10 ns
Min. LE pulse width, tLEW
10 ns
Min LE pulse spacing, tLES
630 ns
Serial clock hold-time from LE, tCKN
10 ns
Hold Time, tPH.
0 ns
Latch Enable Minimum Width, tLEN
10 ns
Setup Time, tPS
2 ns
Parallel Mode (Direct Parallel Mode & Latched Parallel Mode)
Note: The parallel mode is enabled when P/S is set to low.
Direct Parallel Mode - The attenuation state is changed by the Control Voltage Inputs directly. The LE (Latch Enable)
must be at a logic high to control the attenuator in this manner.
Latched Parallel Mode - The attenuation state is selected using the Control Voltage Inputs and set while the LE is in
the Low state. The attenuator will not change state while LE is Low. Once all Control Voltage Inputs are at the desired
states the LE is pulsed. See timing diagram above for reference.
Power-Up States
PUP Truth Table
If LE is set to logic LOW at power-up, the logic state of
PUP1 and PUP2 determines the power-up state of the
part per PUP truth table. If the LE is set to logic HIGH
at power-up, the logic state of D0-D5 determines the
power-up state of the part per truth table. The DVGA
latches in the desired power-up state approximately
200 ms after power-up.
Power-On Sequence
The ideal power-up sequence is: GND, Vdd, digital
inputs, RF inputs. The relative order of the digital
inputs are not important as long as they are powered
after Vdd / GND
PUP1
PUP2
Gain Relative to Maximum
Gain
0
0
0
-31.5
0
1
0
-24
0
0
1
-16
0
1
1
Insertion Loss
1
X
X
0 to -31.5 dB
LE
Note: The logic state of D0 - D5 determines the
power-up state per truth table shown below when LE
is high at power-up.
Truth Table
Control Voltage Input
D5
Control Voltage Table
D4
D3
D2
D1
D0
Gain
Relative to
Maximum
Gain
High
High
High
High
High
High
0 dB
State
Vdd = +3V
Vdd = +5V
High
High
High
High
High
Low
-0.5 dB
Low
0 to 0.5V @ <1 µA
0 to 0.8V @ <1 µA
High
High
High
High
Low
High
-1 dB
High
2 to 3V @ <1 µA
2 to 5V @ <1 µA
High
High
High
Low
High
High
-2 dB
-4 dB
High
High
Low
High
High
High
High
Low
High
High
High
High
-8 dB
Low
High
High
High
High
High
-16 dB
Low
Low
Low
Low
Low
Low
-31.5 dB
Any combination of the above states will provide a reduction in
gain approximately equal to the sum of the bits selected.
For price, delivery and to place orders: Hittite Microwave Corporation, 20 Alpha Road, Chelmsford, MA 01824
Phone: 978-250-3343
Fax: 978-250-3373
Order On-line at www.hittite.com
Application Support: Phone: 978-250-3343 or [email protected]
HMC708LP5 / 708LP5E
v03.0409
0.5 dB LSB 6-BIT DIGITAL
VARIABLE GAIN AMPLIFIER, 1700 - 2200 MHz
Typical Supply Current vs. Vdd (Rbias =
Absolute Maximum Ratings
Vdd (V)
Total Idd (mA)
2.7
191
3.0
3.3
Drain Bias Voltage (Vdd)
5.5 V
206
RF Input Power (RFIN)
(Vdd = +5 Vdc)
-5 dBm + Attenuation State
(do not exceed +10 dBm)
220
Channel Temperature
150 °C
4.5
230
-0.5 to Vdd +0.5V
5.0
252
Digital Inputs (Reset, Shift Clock,
Latch Enable, Serial Input)
5.5
271
Continuous Pdiss (T= 85 °C)
(derate 28 mW/°C above 85 °C)
1.8 W
Thermal Resistance
(channel to ground paddle)
36.2 °C/W
Storage Temperature
-65 to +150 °C
Operating Temperature
-40 to +85 °C
Note: Amplifier will operate over full voltage ranges shown above.
ELECTROSTATIC SENSITIVE DEVICE
OBSERVE HANDLING PRECAUTIONS
Absolute Bias Resistor Range & Recommended Bias Resistor Values for Idd
Vdd
3V
5V
Rbias Ω
Min.
Max.
1K [1]
Open Circuit
0
Open Circuit
Recommended
Total Idd (mA)
2.2k
195
4.7k
201
10k
206
0
231
120
243
270
252
[1] Operation with Vdd= 3V and Rbias < 1K Ohm may result in the part becoming conditionally stable which is not recommended.
For price, delivery and to place orders: Hittite Microwave Corporation, 20 Alpha Road, Chelmsford, MA 01824
Phone: 978-250-3343
Fax: 978-250-3373
Order On-line at www.hittite.com
Application Support: Phone: 978-250-3343 or [email protected]
12
variable gain amplifiers - digital - SMT
270Ω for Vdd= 5V, Rbias= 10kΩ for Vdd= 3V)
12 - 8
HMC708LP5 / 708LP5E
v03.0409
0.5 dB LSB 6-BIT DIGITAL
VARIABLE GAIN AMPLIFIER, 1700 - 2200 MHz
Outline Drawing
Variable gain amplifiers - digital - SMT
12
12 - 9
NOTES:
1. LEADFRAME MATERIAL: COPPER ALLOY
2. DIMENSIONS ARE IN INCHES [MILLIMETERS]
3. LEAD SPACING TOLERANCE IS NON-CUMULATIVE.
4. PAD BURR LENGTH SHALL BE 0.15mm MAXIMUM.
PAD BURR HEIGHT SHALL BE 0.05mm MAXIMUM.
5. PACKAGE WARP SHALL NOT EXCEED 0.05mm.
6. ALL GROUND LEADS AND GROUND PADDLE MUST BE
SOLDERED TO PCB RF GROUND.
7. REFER TO HITTITE APPLICATION NOTE FOR SUGGESTED
LAND PATTERN.
Package Information
Part Number
Package Body Material
Lead Finish
MSL Rating
HMC708LP5
Low Stress Injection Molded Plastic
Sn/Pb Solder
MSL1
[1]
HMC708LP5E
RoHS-compliant Low Stress Injection Molded Plastic
100% matte Sn
MSL1
[2]
Package Marking [3]
H708
XXXX
H708
XXXX
[1] Max peak reflow temperature of 235 °C
[2] Max peak reflow temperature of 260 °C
[3] 4-Digit lot number XXXX
Pin Descriptions
Pin Number
Function
Description
1
RFIN
RF input to the first amplifier (AMP1) This pin is DC coupled
and matched to 50 Ohms.
2, 3, 21, 30
N/C
No connection necessary. These pins may be connected to
RF/DC ground without affecting performance.
4
RES
This pin is used to set the DC current of the first amplifier by
selection of external bias resistor. See application circuit.
Interface Schematic
For price, delivery and to place orders: Hittite Microwave Corporation, 20 Alpha Road, Chelmsford, MA 01824
Phone: 978-250-3343
Fax: 978-250-3373
Order On-line at www.hittite.com
Application Support: Phone: 978-250-3343 or [email protected]
HMC708LP5 / 708LP5E
v03.0409
0.5 dB LSB 6-BIT DIGITAL
VARIABLE GAIN AMPLIFIER, 1700 - 2200 MHz
Pin Descriptions (Continued)
Function
Description
5
SEROUT
Serial input data delayed by 6 clock cycles.
6, 7
PUP1, PUP2
9 - 14
D0 - D5
8
Vdd1
15
P/S
16
CLK
17
SERIN
Interface Schematic
See truth table, control voltage
table and timing diagram.
Supply voltage
See truth table, control voltage
table and timing diagram.
18
LE
19, 23, 25,
26, 28
GND
These pins and package bottom
must be connected to RF/DC ground.
20
RFOUT
RF Output and DC BIAS for the second amplifier (AMP2).
See Application Circuit for off-chip components.
22
RFIN3
RF input for the second amplifier (AMP2).
This pin is DC coupled. An off-chip
DC blocking capacitor is required.
27
RFIN2
24
RFOUT2
29
RFOUT1
RF output for the first amplifier (AMP1)
This pin is matched to 50 Ohms.
31, 32
Vdd2, Vdd3
Power Supply Voltage for the first amplifier. External bypass
capacitors are required. See application circuit.
Input and output of the 6-bit digital attenuator (6-Bit DAT).
These pins are DC coupled and matched to 50 Ohms.
Blocking capacitors are required. Select value based
on lowest frequency of operation.
For price, delivery and to place orders: Hittite Microwave Corporation, 20 Alpha Road, Chelmsford, MA 01824
Phone: 978-250-3343
Fax: 978-250-3373
Order On-line at www.hittite.com
Application Support: Phone: 978-250-3343 or [email protected]
12
variable gain amplifiers - digital - SMT
Pin Number
12 - 10
HMC708LP5 / 708LP5E
v03.0409
0.5 dB LSB 6-BIT DIGITAL
VARIABLE GAIN AMPLIFIER, 1700 - 2200 MHz
Evaluation PCB
Variable gain amplifiers - digital - SMT
12
12 - 11
List of Materials for Evaluation PCB 120493 [1]
Item
Description
Item
Description
J1 - J4
PCB Mount SMA Connector
R12, R13
0 Ohm Resistor, 0402 Pkg.
J5
2mm Vertical Molex 28pos Connector
U1
HMC708LP5(E) Variable Gain Amplifier
C1, C8, C10, C12, C18
220 pF Capacitor, 0402 Pkg.
PCB [2]
120491 Evaluation PCB
C3
10 nF Capacitor, 0402 Pkg.
[1] Reference this number when ordering complete evaluation PCB
C6, C13, C15
1000 pF Capacitor, 0603 Pkg.
[2] Circuit Board Material: Arlon 25FR or Roger 4350
C7, C14
10 nF Capacitor, 0603 Pkg.
C16
27 pF Capacitor, 0603 Pkg.
The circuit board used in the application should use
RF circuit design techniques. Signal lines should
have 50 Ohm impedance while the package ground
leads and exposed paddle should be connected
directly to the ground plane similar to that shown.
A sufficient number of via holes should be used to
connect the top and bottom ground planes. The
evaluation circuit board shown is available from Hittite upon request.
C17
4.7 uF Capacitor, 0805 Pkg.
L2
15 nH Inductor, 0402 Pkg.
L3
6.8 nH Inductor, 0603 Pkg.
L4
47 nH Inductor, 0603 Pkg.
L5
5.1 nH Inductor, 0402
R1 (Rbias)
270 Ohm Resistor, 0402 Pkg.
R2 - R10
39K Ohm Resistor, 0402 Pkg.
For price, delivery and to place orders: Hittite Microwave Corporation, 20 Alpha Road, Chelmsford, MA 01824
Phone: 978-250-3343
Fax: 978-250-3373
Order On-line at www.hittite.com
Application Support: Phone: 978-250-3343 or [email protected]
HMC708LP5 / 708LP5E
v03.0409
0.5 dB LSB 6-BIT DIGITAL
VARIABLE GAIN AMPLIFIER, 1700 - 2200 MHz
Application Circuit
Note 1:
For option 1 (Amp1 + 6-bit DAT only) remove L4. Move 220pF capacitor (0402 Pkg.) from location C10 to C11.
Note 2:
For option 2 (6-Bit DAT + Amp2 only) remove R13, L2, L3 and L5. Move 220pF capacitor (0402 Pkg.) from location
C8 to C9.
For price, delivery and to place orders: Hittite Microwave Corporation, 20 Alpha Road, Chelmsford, MA 01824
Phone: 978-250-3343
Fax: 978-250-3373
Order On-line at www.hittite.com
Application Support: Phone: 978-250-3343 or [email protected]
variable gain amplifiers - digital - SMT
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