HMC7748 Data Sheet
Rev. 0 | Page 8 of 9
APPLICATIONS INFORMATION
The HMC7748 multistage amplifier is designed to be mounted
to a heat sink of a suitable size such that during operation, the
backside case temperature never exceeds 70°C. Operation of the
unit at backside case temperatures greater than 70°C results in
the reduced life of the unit.
Prior to applying dc voltages, terminate both the RF input and
RF output to 50 Ω. Never disconnect the RF output when dc is
applied to the unit.
The EN pin (PA enable) must be tied TTL logic low or to
ground to operate the unit. If the PA enable is not required for
an application, it can be hardwired to ground.
The HMC7748 contains depletion mode devices and has built-in
bias sequencing circuitry, which means that if the 28 V dc voltage
is applied first, there is no damage to the unit.
To turn on the amplifier, complete the following steps:
1. Verify that the dc connections are correct.
2. Verify that the PA enable (EN pin) is pulled high.
3. Verify that the RF input is off.
4. Apply 12 V dc to the 12V pin.
5. Apply 28 V dc to the 28V pin.
6. Pull the PA enable (EN pin) to logic low or to ground.
7. Apply the RF input, ensuring that the power level is less
than −8 dBm.
To turn off the amplifier, complete the following steps:
1. Turn the RF input off.
2. Apply a TTL logic high to the PA enable (EN pin).
3. Turn of f the 28 V dc supply.
4. Turn of f the 12 V dc supply.
