THS4131 datasheet(13/37 Pages) NSC

13 / 37 page

CC) )

CC–

Output Buffer

Vcm Error

Amplifier

Output Buffer

VOUT+

VOUT−

VCC+

VCC−

VIN−

VIN+

30 k

Ω

30 k

Ω

VCC+

VCC−

VOCM

THS4130

THS4131

www.ti.com

SLOS318H

– MAY 2000 – REVISED MAY 2011

APPLICATION INFORMATION

RESISTOR MATCHING

Resistor matching is important in fully-differential amplifiers. The balance of the output on the reference voltage

depends on matched ratios of the resistor. CMRR, PSRR, and cancellation of the second-harmonic distortion

diminish if resistor mismatch occurs. Therefore, it is recommended to use 1% tolerance resistors or better to

keep the performance optimized.

VOCM sets the dc level of the output signals. If no voltage is applied to the VOCMpin, it is set to the midrail voltage

internally defined as:

(1)

In the differential mode, the VOCM on the two outputs cancel each other. Therefore, the output in the differential

mode is the same as the input in the gain of 1. VOCM has a high bandwidth capability up to the typical operation

range of the amplifier. For the prevention of noise going through the device, use a 0.1

µF capacitor on the VOCM

pin as a bypass capacitor. Figure 29 shows the simplified diagram of the THS413x.

Figure 29. THS413x Simplified Diagram

THS4131 Datasheet(PDF) 13 Page - National Semiconductor (TI)