THS4541IRUNR.B datasheet(28/66 Pages) TI2

28 / 66 page

Anything that generates an output common-mode level or shift over temperature also generates an output

differential error term if the two feedback ratios, G1 and G2, are not equal. An error trying to produce a shift in

the output common-mode is overridden by the common-mode control loop, where any feedback ratio mismatch

creates a balanced, differential error around the Vocm output.

The terms that create a differential error from a common-mode term and feedback ratio mismatch include the

desired Vocm voltage, any source common-mode voltage, any drift on the reference bias to the Vocm control

pin, and any internal offset and drift in the Vocm control path.

Considering just the output common-mode control and the source common-mode voltage (Vicm), the conversion

to output differential offsets is done by using Equation 4:

Vocm G1

Vicm G1

Vod

(4)

Neglecting any G1 and G2 mismatch because of standard values approximation, the conversion gain for these

two terms can be recast in terms of the nominal Rf / Rg ≡ G, and tolerance T, as shown in Equation 5. As G

increases, this conversion gain approaches 4T, as a worst-case gain for these terms to output differential offset.

‡

(

)

(

)

Vod

Vocm

(5)

This conversion gain to differential output error is applied to two error terms: Vocm, assuming the input control

pin is driven and not floating, and the source Vicm voltage. The source common-mode voltage is assumed

to be 0 V in this example. If not, apply this gain to the source common-mode value or range in the intended

application.

As a full example of using these terms to estimate the worst-case output 25°C error band, and then the

worst-case drift (by adding all the error terms together independently), use the gain of 2 V/V configuration of

Figure 7-3 with Rf = 402 Ω, and assume ±1% tolerance on the resistors with the standard values used in Figure

7-9.

Rf1

402

Vcc

Rg1

191

Rg2

221

THS4541 Wideband,

Fully-Differential Amplifier

Rf2

402

50-

Input-Matched,

Gain of 2 V/V from Rt,

Single-Ended to Differential,

DC-Coupled, Single Supply

Vocm

500

Vcc

VM1

60.2

FDA

Vcc

Vocm

Vcc

5 V

Vocm

2.5 V

Figure 7-9. DC-Coupled Gain of 2 with Rf = 402 Ω and a Single-Ended to Differential Matched Input 50-Ω

Impedance

The standard value approximation on the signal-input side actually produces added G mismatch along with the

resistor tolerances. For Figure 7-9, G2 = 402 / 221 = 1.819; and G1 = 402 / 218.3 = 1.837 nominally, with a ±2%

tolerance around this initial mismatch for G2 and G1, if 1% resistors are used.

Using the maximum 25°C error terms, and a nominal 2.5-V input to the Vocm control pin, gives Table 7-3 with

the error terms, the gains to the output differential error (Vod), and then the summed output error band at 25°C.

THS4541

SLOS375B – AUGUST 2014 – REVISED FEBRUARY 2024

www.ti.com

Submit Document Feedback

Product Folder Links: THS4541

THS4541IRUNR.B Datasheet(PDF) 28 Page - Texas Instruments

THS4541IRUNR.B Datasheet(HTML) 28 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66

Datasheet Download

Link URL