OPTIMISING THE PERFORMANCE OF THE GX434
1.
Power Supply Considerations
Supply
Voltage
±8
+8/ -12
±12
+12/ -7
Differential Gain
%
(Typical)
Table 1 shows the effect on differential gain (dg) and
differential phase (dp) of various power supply voltages
that may be used. A nominal supply voltage of
±
8
volts result in parameter values as shown in the top
row of the table. By using other power supply voltage
combinations, improvements to these parameters are
possible at the sacrifice of increased chip power
dissipation. Maximum degradation of the differential
gain and phase occurs for the last combination of +12
, -7 volts along with an increase in power dissipation;
these voltages are not recommended.
Differential Phase
degrees
(Typical)
0.030
0.010
0.010
0.084
0.012
0.007
0.007
0.080
Table 2 shows the general characteristic variations
of the GX434 when different combinations of power
supply voltages are used. These changes are rela-
tive to a circuit using
±
8 volts Vcc.
Supply Voltage
±
7
Characteristic Changes
- lower logic thresholds
- max logic I/P (≈ 4.5V)
- loss of off isolation (≈20 dB)
- poorer dg and dp
- slight increase in negative
supply current
- slight decrease in offset
- very similar frequency response
- better dg and dp
- increase in supply current (10%)
- increase in offset (≈ 2-4 mV)
- very similar frequency response
- better dg and dp
- loss in off isolation (≈20 dB)
- poorer dg and dp
+8/ -12
±
12
The GX434 does not require input DC biasing to
optimise dg or dp nor does it need switching
transient suppression at the output. Furthermore,
both the analog signal and logic circuits within the
chip use one common power supply, making power
supply configurations relatively simple and straight-
forward. Several of the input characteristic graphs
on pages 4-5 show that for best operation, the input
bias should be 0 volts. The switching transient
photographs on page 6 show how small the actual
transients are and clearly show the make-before-
break action of the GX434 video multiplexer switch.
+12/ -7
7
510 -34 -2
GENNUM [ GENNUM CORPORATION ]
