THS4281 Datasheet, PDF (24/43 Pages) Texas Instruments – VERY LOW-POWER, HIGH-SPEED, RAIL-TO-RAIL INPUT AND OUTPUT VOLTAGE-FEEDBACK OPERATIONAL AMPLIFIER

THS4281
SLOS432B – APRIL 2004 – REVISED OCTOBER 2015
7 Detailed Description
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7.1 Overview
7.1.1 High-Speed Operational Amplifiers
The THS4281 is a unity gain stable, rail-to-rail input and output, voltage-feedback operational amplifier designed
to operate from a single 2.7-V to 16.5-V power supply.
7.2 Feature Description
7.2.1 Wideband, Noninverting Operation
Figure 68 shows the noninverting gain configuration of 2 V/V used to demonstrate the typical performance
curves.
Voltage feedback amplifiers can use a wide range of resistors values to set their gain with minimal impact on
frequency response. Larger-valued resistors decrease loading of the feedback network on the output of the
amplifier, but may cause peaking and instability. For a gain of +2, feedback resistor values between 1 kΩ and 4
kΩ are recommended for most applications. However, as the gain increases, the use of even higher feedback
resistors can be used to conserve power. This is due to the inherent nature of amplifiers becoming more stable
as the gain increases, at the expense of bandwidth. Figure 73 and Figure 74 show the THS4281 using feedback
resistors of 10 kΩ and 100 kΩ. Be cautioned that using such high values with high-speed amplifiers is not
typically recommended, but under certain conditions, such as high gain and good high-speed printed circuit
board (PCB) layout practices, such resistances can be used.
+V_S
50-W Source
V_I
+
49.9 W
_
2.49 kW R_g
R_f
2.49 kW
+
0.1 µF 6.8 µF
V_O
To Load
0.1 µF 6.8 µF
+
−V_S
Figure 68. Wideband, Noninverting Gain Configuration
7.2.2 Wideband, Inverting Operation
Figure 69 shows a typical inverting configuration where the input and output impedances and noise gain from
Figure 68 are retained with an inverting circuit gain of –1 V/V.
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