3
ISOMET
The amplitude-modulated MMIC output drives the input to a DMOS FET based power amplifier. This
amplifier is designed to operate at full rated power into a 50
load with 100% duty cycle.
Figure 3 illustrates the principal waveforms of the 750c Driver.
Conduction cooling of the driver from the mounting face to a heat sink or forced-air convection cooling
is mandatory. The mounting face temperature must not exceed 70
C.
SERIOUS DAMAGE TO THE AMPLIFIER MAY RESULT IF THE TEMPERATURE EXCEEDS 70
C.
SERIOUS DAMAGE TO THE AMPLIFIER MAY ALSO RESULT IF THE RF OUTPUT CONNECTOR
IS OPERATED OPEN-CIRCUITED OR SHORT-CIRCUITED.
All 750c series drivers require a stable d-c power for operation. The required voltage is +24 / 28Vdc
at a current drain of approximately 470mA EXCEPT model 750c-L. This lower power driver operates
from 15Vdc. The external power source should be regulated to
2% and the power supply ripple
voltage should be less than 25mV for best results.
2.
MODULATION
The 750 Series Modulator Driver, features one control for the RF POWER ADJUST and two
modulation inputs.
D-Mod
and
A-Mod.
The RF POWER ADJUST control sets the peak driver output for fully ON condition
RF output fully “ON” requires
both
D-Mod
= TTL high and
A-Mod
= 5V.
RF output “OFF” requires
either
input
D-Mod
= TTL low or
A-Mod
= 0V.
Typical switching and latency timing
Variants
Active Input
trd
tfd
tr
Tf
C-L, C-2
D-Mod
30nsec 30nsec 10nsec
5nsec
A-Mod
5nsec
5nsec
10nsec 10nsec
C-4, C-6
D-Mod
30nsec 30nsec 12nsec
5nsec
A-Mod
5nsec
5nsec
16nsec 16nsec
tr
tf
trd
Modulation Input
tfd
RF Output
