THS6062IDR Datasheet, PDF (17/36 Pages) Texas Instruments – LOW-NOISE ADSL DUAL DIFFERENTIAL RECEIVER

THS6062
www.ti.com
SLOS228D – JANUARY 1999 – REVISED OCTOBER 2007
APPLICATION INFORMATION
THEORY OF OPERATION
The THS6062 is a high-speed, operational amplifier configured in a voltage-feedback architecture. It is built using
a 30-V, dielectrically isolated, complementary bipolar process with NPN and PNP transistors possessing f_Ts of
several GHz. This results in an exceptionally high-performance amplifier that has a wide bandwidth, high slew
rate, fast settling time, and low distortion. A simplified schematic is shown in Figure 39.
(7) V_CC +
IN − (2,6)
(1,7) OUT
IN + (3,5)
Figure 39. THS6062 Simplified Schematic
(4) V_CC −
The ADSL remote terminal receive band consists of 255 separate carrier frequencies each with its own
modulation and amplitude level. With such an implementation, it is imperative that signals received off the
telephone line have as high a signal-to-noise ratio (SNR) as possible. This is because of the numerous sources
of interference on the line. The best way to accomplish this high SNR is to have a low-noise receiver on the
front-end. It is also important to have the lowest distortion possible to help minimize against interference within
the ADSL carriers. The THS6062 was designed with these two priorities in mind.
By taking advantage of the superb characteristics of the complimentary bipolar process (BICOM), the THS6062
offers extremely low noise and distortion while maintaining a high bandwidth. There are some aspects that help
minimize distortion in any amplifier. The first is to extend the bandwidth of the amplifier as high as possible
without peaking. This allows the amplifier to eliminate any nonlinearities in the output signal. Another thing that
helps to minimize distortion is to increase the load impedance seen by the amplifier, thereby reducing the
currents in the output stage. This will help keep the output transistors in their linear amplification range and will
also reduce the heating effects. This can be seen in Figure 18 to Figure 21, which show a 1-kΩ load distortion is
much better than a 150-Ω load.
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