THS1060

10-BIT 60 MSPS IF SAMPLING COMMUNICATIONS

ANALOG-TO-DIGITAL CONVERTER

SLAS212 – MARCH 2000

17

POST OFFICE BOX 655303

APPLICATION INFORMATION

using the analog input

The THS1060 obtains optimum performance when the analog signal inputs are driven differentially. The circuit

below shows the optimum configuration, see Figure 23. The signal is fed to the primary of an RF transformer.

Since the input signal must be biased around the common mode voltage of the internal circuitry, the common

a 0.1

µF and 0.01 µF low inductance capacitor.

R

VIN+

VCM

THS1060

0.01

µF

0.1

µF

50

Ω

1:1

VIN–

50

Ω

ac Signal

T1-1T

Figure 23. THS1060 With Coaxial Feed

When it is necessary to buffer or apply a gain to the incoming analog signal, it is also possible to combine a

single-ended amplifier with an RF transformer as shown in Figure 24. For this application, a wide-band current

mode feedback amplifier such as the THS3001 is best. The single ended output allows the use of standard

passive filters between the amplifier output and the primary. In this case, the SFDR of the op amp is not as critical

as that of the A/D converter. While harmonics generated from within the A/D converter fold back into the first

Nyquist zone, harmonics generated externally in the op amps can be filtered out with passive filters.

VIN+

VIN–

VCM

THS1060

0.1

µF

0.01

µF

_

+

BPF

10

Ω

1 k

Ω

1 k

Ω

RT

IF Input

THS3001

Impedance Ratio = 1:n

Figure 24. IF Input Buffered with THS3001 Op Amp