THS4524-EP Datasheet, PDF (29/48 Pages) Texas Instruments – VERY LOW POWER, NEGATIVE RAIL INPUT, RAIL-TO-RAIL OUTPUT, FULLY DIFFERENTIAL AMPLIFIER

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Low-Power Applications and the Effects of
Resistor Values on Bandwidth
For low-power operation, it may be necessary to
increase the gain setting resistors values to limit
current consumption and not load the source. Using
larger value resistors lowers the bandwidth of the
THS4524 as a result of the interactions between the
resistors, the device parasitic capacitance, and
printed circuit board (PCB) parasitic capacitance.
Figure 65 shows the small-signal frequency response
with 1-kΩ, 10-kΩ, and 100-kΩ resistors for R_F, R_G,
and R_L (impedance is assumed to typically increase
for all three resistors in low-power applications).
SMALL-SIGNAL FREQUENCY RESPONSE
Gain = 1, R_F = R_G = R_L = 1 kW, 10 kW, 100 kW
6
3
1 kW
0
-3
10 kW
-6
-9
100 kW
-12
-15
-18 V_S+ = 5.0 V
-21 ^VO ^{= 100 mV}PP
Gain = 1 V/V
-24
0.1
1
10
100
Frequency (MHz)
1000
Figure 65. THS4524 Frequency Response with
Various Gain Setting and Load Resistor Values
THS4524-EP
SBOS609A – JUNE 2012 – REVISED AUGUST 2013
Frequency Response Variation due to
Package Options
Users can see variations in the small-signal (V_OUT =
100 mV_PP) frequency response between the available
package options for the THS452x family as a result of
parasitic elements associated with each package and
board layout changes. Figure 66 shows the variance
measured in the lab; this variance is to be expected
even when using a good layout.
SMALL-SIGNAL FREQUENCY RESPONSE
Device and Package Option Comparison
6
THS4522,
3
THS4524
0
THS4521
-3
THS4521
SOIC
MSOP
-6
-9
-12
-15 _{VS+ = 5.0 V}
-18 ^{Gain = 1 V/V}
-21
R_F = 1 kW
R_L = 1 kW
-24
0.1
1
10
100
1000
Frequency (MHz)
Figure 66. Small-Signal Frequency Response:
Package Variations
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