9
Amp
Input
Vdd
Output
Output
Pad
Ground
Pad
Input
Pad
50 Ohm line 50 Ohm line
100 pF
0.1 uF
15 nH
Vc
0.1 uF
100 pF
22 nH
100 pF
Figure 19. Example application of VMMK-2103 at 3GHz
Figure 20. Evaluation/Test Board (available to quali ed customer request)
VMMK-2103 Application and Usage
(Please always refer to the latest Application Note AN5378 in website)
Biasing and Operation
The VMMK-2103 can be used as a low noise ampli er or as a
driver ampli er. The nominal bias condition for the VMMK-
2103 is Vd = Vc = 5V. At this bias condition, the device provides
an optimal compromise between power consumption, noise
gure, gain, power output, and OIP3. The VMMK-2103 is
biased with a positive supply connected to the output pin Vd
through an external user supplied bias decoupling network
as shown in Figure 19. A control voltage Vc is applied to
the input pin through a similar bias decoupling network.
The VMMK-2103 operates in the gain mode when Vc=Vd.
Nominal Vd is between 3 and 5 V. When Vc is at 0V, the device
is biased in the “bypass” mode, which engages the integrated
bypass switch which then shuts down the ampli er.
The parallel combination of the 100pF and 0.1uF capacitors
provide a low impedance in the band of operation and at
lower frequencies and should be placed as close as possible
to the inductor. The low frequency bypass provides good
rejection of power supply noise and also provides a low
impedance termination for third order low frequency mixing
products that will be generated when multiple in-band
signals are injected into any ampli er.
The input bias decoupling network is similar to that used on
the output. A 22 nH inductor bypass with a 100pF capacitor
provides a means to control Vc on the input port. Since there
is a voltage developed internally to the VMMK-2103 at the
input terminal, any resistance in series with the power supply
will actually raise the input terminal above ground enough
that it begins to a ect linearity in the bypass mode. Switching
time between the gain mode and the bypass mode is under
0.1 sec. If switching speed is not a high priority, then the
bypass capacitor on the input should be raised to 0.1 uF to
help minimize noise and spurious from the power supply
adversely a ecting the operation of the VMMK-2103.
S Parameter Measurements
The S-parameters are measured on a .016 inch thick RO4003
printed circuit test board, using G-S-G (ground signal
ground) probes. Coplanar waveguide is used to provide a
smooth transition from the probes to the device under test.
The presence of the ground plane on top of the test board
results in excellent grounding at the device under test. A
combination of SOLT (Short - Open - Load - Thru) and TRL
(Thru - Re ect - Line) calibration techniques are used to
correct for the e ects of the test board, resulting in accurate
device S-parameters. The reference plane for the S Param-
eters is at the edge of the package.
The product consistency distribution charts shown on
page 2 represent data taken by the production wafer probe
station using a 300um G-S wafer probe. The ground-signal
probing that is used in production allows the device to be
probed directly at the device with minimal common lead
inductance to ground. Therefore there will be a slight dif-
ference in the nominal gain obtained at the test frequency
using the 300um G-S wafer probe versus the 300um G-S-G
printed circuit board substrate method.
The output bias decoupling network can be easily con-
structed using small surface mount components. The value
of the output inductor can have a major e ect on both
low and high frequency operation. The demo board uses
a 15 nH inductor that has a self resonant frequency higher
than the maximum desired frequency of operation. If the
self-resonant frequency of the inductor is too close to the
operating band, the value of the inductor will need to be
adjusted so that the self-resonant frequency is signi cantly
higher than the highest frequency of operation.
Typically a passive component company like Murata does
not specify S parameters at frequencies higher than 5 or
6 GHz for larger values of inductance making it di cult
to properly simulate ampli er performance at higher
frequencies. It has been observed that the Murata LQW15AN
series of 0402 inductors actually works quite well above their
normally speci ed frequency. As an example, increasing the
output inductor from 15 nH to 39 nH provides bandwidth
from 200 MHz through 6 GHz with good gain atness.
Further extending the low frequency response of the VMMK-
2103 is possible by using two di erent value inductors in
series with the smaller value inductor placed closest to the
device and favoring the higher frequencies. The larger value
inductor will then o er better low frequency performance by
not loading the output of the device.