THS4521 datasheet(30/53 Pages) TI2

30 / 53 page

Using these expressions to generate a swept gain table of values results in Table 10-1, where the best standard

1% resistor values are shown to minimize input impedance and gain error to target.

Table 10-1. Swept Gain 50-Ω Input Match with RF = 1.5-kΩ (±1 Standard Values)

GAIN (V/V)

RG1

RG2

ZIN

0.1

1500

15000

49.9

15000

49.74

0.09973

1500

51.1

1500

49.82

0.994

1500

750

52.3

768

49.98

1.978

1500

287

54.9

316

49.6

5.014

1500

137

61.9

165

50.4

10.08

Where an input impedance match is not required, simply set the input resistor to obtain the desired gain without

an additional resistor to ground (remove RT in Figure 10-3). This scenario is common when coming from the

output of another single-ended op amp (such as the OPA810 or OPA192). This single-ended to differential stage

shows a higher input impedance than the physical RG as given by the expression for ZA (active input impedance)

shown as Equation 4.

·§

¸¨

¹©

(4)

Using Equation 4 for the gain of 1 V/V with all resistors equal to 1.5-kΩ shows an input impedance of 2 kΩ. The

increased input impedance comes from the common-mode input voltage at the amplifier pins moving in the

same direction as the input signal. The common-mode input voltage must move to create the current in the non-

signal input RG resistor to produce the inverted output. The current flow into the signal-side input resistor is

impeded because the common-mode input voltage moves with the input signal, thus increasing the apparent

input impedance in the signal input path.

THS4561

SBOS874D – AUGUST 2017 – REVISED FEBRUARY 2021

www.ti.com

Submit Document Feedback

Product Folder Links: THS4561

THS4521 Datasheet(PDF) 30 Page - Texas Instruments

THS4521 Datasheet(HTML) 30 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

Datasheet Download

Link URL