AD8565/AD8566/AD8567

Rev. D | Page 11 of 16

TOTAL HARMONIC DISTORTION + NOISE (THD+N)

LCD PANEL APPLICATIONS

The AD856x amplifier is designed for LCD panel applications

or applications where large capacitive load drive is required. It

can instantaneously source/sink greater than 250 mA of current. At

unity gain, it can drive 1 μF without compensation. This makes

The AD856x family features low total harmonic distortion.

Figure 31 shows THD+N vs. frequency. The THD+N for the

AD856x over the entire supply range is below 0.008%. When

the device is powered from a 16 V supply, the THD+N stays

below 0.003%. Figure 31 shows the AD8566 in a unity

noninverting configuration.

To evaluate the performance of the AD856x family, a test circuit

LCD panel.

FREQUENCY (Hz)

20

100

10

1

0.01

0.1

1k

10k

30k

Figure 32 shows the test circuit. Series capacitors and resistors

connected to the output of the op amp represent the load of the

LCD panel. The 300 Ω and 3 kΩ feedback resistors are used to

improve settling time. This test circuit simulates the worst-case

scope photo of the instantaneous output peak current capability

of the AD856x family.

INPUT 0VTO 8V

SQUARE WAVE WITH

15.6µs PULSE WIDTH

300Ω

3kΩ

10Ω

10Ω

10Ω

10Ω

10nF

10nF

10nF

10nF

MEASURE

CURRENT

4V

8V

10Ω TO 20Ω

Figure 31. THD+N vs. Frequency

SHORT-CIRCUIT OUTPUT CONDITIONS

The AD856x family does not have internal short-circuit

protection circuitry. As a precautionary measure, it is

recommended not to short the output directly to the

positive power supply or to ground.

It is not recommended to operate the AD856x with more than

35 mA of continuous output current. The output current can be

limited by placing a series resistor at the output of the amplifier

whose value can be derived using

TIME (2µs/DIV)

CH 2 = 100mA/DIV

CH 1 = 5V/DIV

10

0%

100

90

mA

35

S

X

V

R ≥

value of 143 Ω.