THS6212 Datasheet, PDF (29/48 Pages) Texas Instruments – Differential, Line-Driver Amplifier

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8 Application and Implementation
THS6212
SBOS758 – MAY 2016
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
The THS6212 is typically used to drive high output power applications with various load conditions. In the Typical
Applications section, the amplifier is presented in a general-purpose, wideband, current-feedback configuration,
and a more specific 100-Ω twisted pair cable line driver. However, the amplifier is also applicable for many
different general-purpose and specific cable line-driving scenarios beyond what is shown in the Typical
Applications section.
8.2 Typical Applications
8.2.1 Wideband Current-Feedback Operation
The THS6212 provides the exceptional ac performance of a wideband current-feedback op amp with a highly
linear, high-power output stage. Requiring only 21 mA of quiescent current, the THS6212 swings to within 1.9 V
of either supply rail on a 100-Ω load and delivers in excess of 416 mA at room temperature. This low-output
headroom requirement, along with biasing that is independent of the supply voltage, provides a remarkable ±6-V
supply operation. The THS6212 delivers greater than 140-MHz bandwidth driving a 2-V_PP output into 100 Ω on a
±6-V supply. Previous boosted output stage amplifiers typically suffer from very poor crossover distortion when
the output current goes through zero. The THS6212 achieves a comparable power gain with improved linearity.
The primary advantage of a current-feedback op amp over a voltage-feedback op amp is that ac performance
(bandwidth and distortion) is relatively independent of signal gain. Figure 81 shows the dc-coupled, gain of
10 V/V, dual power-supply circuit configuration used as the basis of the ±12-V Electrical Characteristics tables
and Typical Characteristics sections.
12 V
D1
THS6212
R_F
1.24 kW
V_IN
R_G
R_F
274 W 1.24 kW
R_L V_OUT
D2
THS6212
-12 V
G_DIFF = 1 +
2 ´ R_F
R_G
= ^VOUT
V_IN
Copyright © 2016, Texas Instruments Incorporated
Figure 81. Noninverting Differential I/O Amplifier
8.2.1.1 Design Requirements
The main design requirements for wideband current-feedback operation are to choose power supplies that satisfy
common-mode requirements at the input and output of the device, and also to use a feedback resistor value that
allows for the proper bandwidth when maintaining stability. These requirements and the proper solutions are
described in the Detailed Design Procedure section. Using transformers and split power supplies can be required
for certain applications.
Copyright © 2016, Texas Instruments Incorporated
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