Power supply considerations TSH350
12/22
4 Power supply considerations
Correct power supply bypassing is very important for optimizing performance in high-
frequency ranges. Bypass capacitors should be placed as close as possible to the IC pins to
improve high-frequency bypassing. A capacitor greater than 1μF is necessary to minimize
the distortion. For better quality bypassing, a capacitor of 10nF can be added which should
also be placed as close as possible to the IC pins.
Bypass capacitors must be incorporated for both the negative and the positive supply.
Note: On the SO8_SINGLE_HF board, these capacitors are C6, C7, C8, C9.
Figure 30. Circuit for power supply bypassing
Single power supply
In the event that a single supply system is used, biasing is necessary to obtain a positive
output dynamic range between 0V and +V
CC
supply rails. Considering the values of V
OH
and V
OL
, the amplifier will provide an output swing from +0.9V to +4.1V on a 100Ω load.
The amplifier must be biased with a mid-supply (nominally +V
CC
/2), in order to maintain the
DC component of the signal at this value. Several options are possible to provide this bias
supply, such as a virtual ground using an operational amplifier or a two-resistance divider
(which is the cheapest solution). A high resistance value is required to limit the current
consumption. On the other hand, the current must be high enough to bias the non-inverting
input of the amplifier. If we consider this bias current (35μA maximum) as 1% of the current
through the resistance divider, to keep a stable mid-supply, two resistances of 750Ω can be
used.
The input provides a high-pass filter with a break frequency below 10Hz which is necessary
to remove the original 0 volt DC component of the input signal, and to fix it at +V
CC
/2.
Figure 31 illustrates a 5V single power supply configuration for the SO8_S_MULTI
evaluation board (see Evaluation boards on page 11).
+
-V
CC
+V
CC
10µF
+
10nF
10µF
+
10nF
-
+
-V
CC
+V
CC
10µF
+
10nF
10µF
+
10nF
-
Obsolete Product(s) - Obsolete Product(s)
