MMS005AA
DC to 40 GHz MMIC Medium Power
Voltage Controlled Attenuator
Features
• Wideband operation: DC to 40 GHz
• Low Insertion Loss (<3 dB)
• Good Input/Output Match
• Medium Attenuation (max. 17 dB)
• Size: 1640 x 920 mm
Description
The MMS005AA is a medium-power
DC-40 GHz PHEMT FET attenuator.
The performance of the device is con-
trolled by two bias voltages, Vseries
and Vshunt. The bias voltages control
the match and attenuation of the device
when varied between -1V and +0.5V
DC. For additional information please
refer to the tables of recommended bias
settings optimized for flat insertion loss
and flat attenuation.
Application
The MMS005AA MMIC voltage controlled
attenuator is ideal for high frequency and
broadband applications in test equipment,
commercial and military systems. The
attenuator is especially suited for applications
needing a moderate amount of adjustable
attenuation and fast attenuation control from
DC to millimeter frequencies. The device
is also useful as a general purpose building
block in communications systems.
Key Characteristics:
Zo=50Ω
Parameter
Attenuation (dB)
Flatness (±dB)
Insertion Loss (dB
S11 (dB)
S22 (dB)
P1dB (dBm)
Description
DC to 40 GHz
DC to 40 GHz
DC to 40 GHz
DC to 40 GHz
DC to 40 GHz
1dB Gain Compression 0 to 15 dB Attenuation
Min
0
-
-
-
-
8
Typ
-
1
-
-10
-10
-
Max
17
-
3
-8
-8
-
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MMS005AA
Optimized for Flat Attenuation (Typical)
MMS005AA Attenuation
Vseries (V)
-0.625
-0.625
-0.625
-0.616
-0.608
-0.601
-0.595
-0.569
-0.55
Typical on wafer measured performance
Vshunt (V)
0.343
-0.287
-0.1
-0.456
-0.501
-0.544
-0.583
-0.622
-0.7
-1
Att. (dB)*
18.3
15.9
13.6
11.6
9.6
7.5
5.7
3.8
1.8
0
0.5
Optimized for Flat Insertion Loss (Typical)
MMS005AA Insertion Loss
Vseries (V)
-650
-0.65
-0.65
-0.65
-0.641
-0.618
0.595
-0.568
-0.55
Typical on wafer measured performance
Vshunt (V)
0
-0.312
-0.413
-0.475
-0.513
-0.549
-0.583
-0.624
-0.7
-1
Att. (dB)*
19.2
16.9
14.6
12.4
10.7
8.9
7.1
5.1
3.3
1.4
0.5
Note: (*) Midband
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MMS005AA
MMS005AA S11
MMS005AA S22
Typical on wafer measured performance
Typical on wafer measured performance
Table 1: Supplemental Specifications
Parameter
Vseries
Vshunt
Dcin
Dcout
GND
Tch
Θch
Description
Attenuation Control Voltage
Attenuation Control Voltage
DC feedback circuit input
DC feedback circuit output
Backside Ground Plane
Channel Temperature
Thermal Resistance (Tcase=85°C)
Min
-2V
-2V
0V
0V
-
-
-
Typ
-
-
0.25 V
0.25 V
-
-
60o C/Watt
Max
0.5V
0.5V
1V
1V
22dBm
150°C
-
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MMS005AA
Typical Pin (1dB) vs Attenuation
MMS005AA Simplified Schematic Diagram
Typical on evaluated package measured performance
Pick-up and Chip Handling:
This MMIC has exposed air bridges on the top surface.
Do not pick up chip with vacuum
on the die center;
handle from edges or use a collet.
ESD Handling and Bonding:
This MMIC is ESD sensitive;
preventive measures should be taken during handling, die attach,
and bonding.
Epoxy die attach is recommended.
Please review our application note MM-APP-0001
handling and die attach recommendations, on our website for more handling, die attach
and bonding information.
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MMS005AA
DC Feedback Circuit for Variable Attenuator:
The following feedback circuit does a good job of providing the series and shunt biases to the variable
attenuator for a user-selected amount of attenuation.
The circuit references a 1/3 scale version of the microwave attenuator, which is used for the
DC feedback loop. Because the devices are 1/3 the size of the unscaled attenuator, the reference
impedence is 3 times larger (150W instead of 50W).
The circuit uses two ordinary opamps to provide the bias control voltages to the attenuator. Opamp
OA1 senses the input impedance of the attenuator and adjusts the series FET gate voltage Vseries
so that the impedance looking into the attenuator is 150W. The input impedance can be adjusted with
the potentiometer shown in the schematic (Figure 8). When this feedback loop is at DC equilibrium
the voltage at DCin will be Vref/2.
The second opamp OA2 adjusts the shunt FET gate voltage so that the DC output voltage DCout
is equal to the voltage at the opamp negative input terminal. When 0V is applied to the negative
input terminal of OA2, the attenuation is maximized.
Conversely, if Vref/2 is applied at the negative input of OA2 then the attenuation is minimized.
A voltage divider with the shunt resistor terminated by the voltage Vref makes for a convienient
conversion of voltage to attenuation. If the input to the divider Vatten is set to 0 volts then the
negative input of OA2 will have a value of Vref/2 and the attenuator will have minimum attenuation.
Conversely, if Vatten is set to –Vref then the negative input of OA2 is set 0V and the attenuator
will have maximum attenuation. This makes the calculation of Vatten easy and requires a minimum
number of parts.
Scaled DC Attenuator
Circuit (1/3 scale attenuator)
The DC feedback circuit to adjust the attenuator
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