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ADA4895-2

Data Sheet

Rev. 0 | Page 20 of 24

APPLICATIONS INFORMATION

USING THE ADA4895-2 AT A GAIN < +10

The ADA4895-2 is minimum gain 10 stable when used in normal

gain configurations. However, the ADA4895-2 can be configured

to work at lower gains down to a gain of +5. Figure 43 shows how

to add a simple RC circuit (R1 = 49.9 Ω and C1 = 60 pF) to allow

the ADA4895-2 to operate at a gain of +5.

VOUT

150pF

50Ω

60pF

Ω

VIN

Ω

200

Ω

Figure 43. Configuring the ADA4895-2 for a Gain of +5 Stable

This circuit has a gain of 9 at high frequency and a gain of 5

at frequencies lower than the resonance frequency of 53 MHz

(1/2πR1C1). With a noise gain of approximately 9 at high frequency,

the total output noise increases unless an antialiasing filter is used

to block the high frequency content.

Figure 44 shows the small and large signal frequency response of

the circuit shown in Figure 43 into a 50 Ω analyzer (G = +5 V/V

or 14 dB). As shown in Figure 44, the circuit is very stable, and

the peaking is a little over 2 dB. This configuration is scalable to

accommodate any gain from 5 to 10, as shown in Table 9.

–1

0.1

100

1000

FREQUENCY (MHz)

VOUT = 30mV p-p

VOUT = 2V p-p

VOUT = 250mV p-p

VS = ±5V

G = +5

Figure 44. Frequency Response for G = +5

Table 9. Component Values Used with the ADA4895-2 for Gain < +10

Gain

T (Ω)

1 (Ω)

1 (pF)

G (Ω)

F (Ω)

O (Ω)

L (pF)

49.9

200

49.9

150

49.9

66.5

40.2

200

49.9

150

49.9

110

37.4

226

49.9

150

49.9

205

32.4

226

49.9

120

49.9

30.9

249

49.9

100

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