ADA4898-2YRDZ-R7 datasheet(15/20 Pages) AD

15 / 20 page

Data Sheet

ADA4898-1/ADA4898-2

Rev. D | Page 15 of 20

APPLICATIONS INFORMATION

HIGHER FEEDBACK RESISTOR GAIN OPERATION

The ADA4898 schematic for the noninverting gain

configuration shown in Figure 47 is nearly a textbook example.

The only exception is the feedback capacitor in parallel with

the feedback resistor, RF, but this capacitor is recommended

only when using a large RF value (>300 Ω). Figure 48 shows the

difference between using a 100 Ω resistor and a 1 kΩ feedback

resistor. Due to the high input capacitance in the ADA4898 when

using a higher feedback resistor, more peaking appears in the

closed-loop gain. Using the lower feedback resistor resolves this

issue; however, when running at higher supplies (±15 V) with

an RF of 100 Ω, the system draws a lot of extra current into the

feedback network. To avoid this problem, a higher feedback

resistor can be used with a feedback capacitor in parallel. Figure 48

shows the effect of placing a feedback capacitor in parallel with

a larger RF. In this gain-of-2 configuration, RF = RG = 1 kΩ and

CF = 2.7 pF. When using CF, the peaking drops from 6 dB to less

than 2 dB.

VIN

VOUT

10µF

+VS

–VS

10µF

0.1µF

Figure 47. Noninverting Gain Schematic

–15

–12

–9

–6

–3

FREQUENCY (Hz)

100k

10M

100M

RF = 1kΩ, CF = 2.7pF

RF = 1kΩ

RF = 100Ω

G = +2

RL = 1kΩ

VS = ±15V

Figure 48. Small Signal Frequency Response for

Various Feedback Impedances

RECOMMENDED VALUES FOR VARIOUS GAINS

Table 8 provides a useful reference for determining various gains

and associated performance. RF is set to 100 Ω for gains greater

than 1. A low feedback RF resistor value reduces peaking and

minimizes the contribution to the overall noise performance

of the amplifier.

Table 8. Gains and Recommended Resistor Values Associated with Them (Conditions: VS = ±5 V, TA = 25°C, RL = 1 kΩ, RT = 49.9 Ω)

Gain

RF (Ω)

RG (Ω)

−3 dB SS BW (MHz),

VOUT = 100 mV p-p

Slew Rate (V/µs),

VOUT = 2 V Step

ADA4898 Voltage

Noise (nV/√Hz), RTO

Total System Noise

(nV/√Hz), RTO

N/A

0.9

1.29

100

1.8

3.16

100

24.9

4.5

7.07

ADA4898-2YRDZ-R7 bảng dữ liệu(PDF) 15 Page - Analog Devices

ADA4898-2YRDZ-R7 bảng dữ liệu(HTML) 15 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

bảng dữ liệu tải về

Link URL