AD8226ARMZ-R7 datasheet(24/29 Pages) AD

24 / 29 page

Data Sheet

AD8226

Rev. C | Page 23 of 28

APPLICATIONS INFORMATION

DIFFERENTIAL DRIVE

+IN

–IN

REF

AD8226

VBIAS

–

OP AMP

+OUT

–OUT

RECOMMENDED OP AMPS: AD8515, AD8641, AD820.

RECOMMENDED R V

ALUES: 5kΩ to 20kΩ.

Figure 64. Differential Output Using an Op Amp

Figure 64 shows how to configure the AD8226 for differ-

ential output.

The differential output is set by the following equation:

VDIFF_OUT = VOUT+ − VOUT− = Gain × (VIN+ − VIN−)

The common-mode output is set by the following equation:

VCM_OUT = (VOUT+ − VOUT−)/2= VBIAS

The advantage of this circuit is that the dc differential accuracy

depends on the AD8226, not on the op amp or the resistors. In

addition, this circuit takes advantage of the precise control that the

AD8226 has of its output voltage relative to the reference voltage.

Although the dc performance and resistor matching of the op amp

affect the dc common-mode output accuracy, such errors are

likely to be rejected by the next device in the signal chain and

therefore typically have little effect on overall system accuracy.

Tips for Best Differential Output Performance

For best ac performance, an op amp with at least a 2 MHz gain

bandwidth and a 1 V/µs slew rate is recommended. Good choices

for op amps are the AD8641, AD8515, and AD820.

Keep trace lengths from the resistors to the inverting terminal

of the op amp as short as possible. Excessive capacitance at this

node can cause the circuit to be unstable. If capacitance cannot

be avoided, use lower value resistors.

For best linearity and ac performance, a minimum positive

supply voltage (+VS) is required. Table 9 shows the minimum

supply voltage required for optimum performance. In this mode,

VCM_MAX indicates the maximum common-mode voltage expected

at the input of the AD8226.

Table 9. Minimum Positive Supply Voltage

Temperature

Equation

Less than −10°C

S > (VCM_MAX + VBIAS)/2 + 1.4 V

−10°C to 25°C

S > (VCM_MAX + VBIAS)/2 + 1.25 V

More than 25°C

S > (VCM_MAX + VBIAS)/2 + 1.1 V

AD8226ARMZ-R7 数据表(PDF) 24 Page - Analog Devices

AD8226ARMZ-R7 数据表(HTML) 24 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 21 22 23 24 25 26 27 28 29

数据表下载