AD8051/AD8052/AD8054

–12–

REV. B

Overdrive Recovery

Overdrive of an amplifier occurs when the output and/or input

range are exceeded. The amplifier must recover from this over-

drive condition. As shown in Figure 36, the AD8051/AD8052/

AD8054 recovers within 60 ns from negative overdrive and

within 45 ns from positive overdrive.

Figure 36. Overdrive Recovery

Driving Capacitive Loads

Consider the AD8051/AD8052 in a closed-loop gain of +1 with

Ω in parallel with 50 pF. Figures 37

and 38 show its frequency and time domain responses, respec-

tively, to a small-signal excitation. The capacitive load drive of

the AD8051/AD8052/AD8054 can be increased by adding a

low valued resistor in series with the load. Figures 39 and 40

show the effect of a series resistor on capacitive drive for varying

voltage gains. As the closed-loop gain is increased, the larger

phase margin allows for larger capacitive loads with less peak-

ing. Adding a series resistor with lower closed-loop gains ac-

complishes the same effect. For large capacitive loads, the

frequency response of the amplifier will be dominated by the

roll-off of the series resistor and the load capacitance.

FREQUENCY – MHz

500

0.1

1

10

100

G = +1

8

6

4

2

0

2

4

6

8

10

Figure 37. AD8051/AD8052 Closed-Loop Frequency

2.60

2.55

2.50

2.45

2.40

Figure 38. AD8051/AD8052 200 mV Step Response:

30%

OVERSHOOT

100mV STEP

50

10000

1000

1

16

2

345

100

10

Figure 39. AD8051/AD8052 Capacitive Load Drive vs.

Closed-Loop Gain

30%

OVERSHOOT

100mV STEP

50

1000

100

10

16

2

345

Figure 40. AD8054 Capacitive Load Drive vs. Closed-Loop

Gain

Circuit Description

The AD8051/AD8052/AD8054 is fabricated on Analog Devices’

proprietary eXtra-Fast Complementary Bipolar (XFCB) pro-

cess, which enables the construction of PNP and NPN transis-

dielectrically isolated to eliminate the parasitic and latch-up