OPA607 datasheet(16/43 Pages) TI

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8.3 Feature Description

8.3.1 Operating Voltage

The OPAx607 operational amplifiers are fully specified and assured for operation from 2.2 V to 5.5 V, applicable

from –40°C to +125°C. The OPAx607 devices are completely operational with asymmetric, symmetric and single

supply voltages applied across the supply pins. The total voltage (that is, (VS+) – (VS–)) must be less than the

supply voltage mentioned in Section 7.1.

8.3.2 Rail-to-Rail Output and Driving Capacitive Loads

Designed as a low-power, low-voltage operational amplifier, the OPAx607 devices are capable of delivering a

robust output drive. For resistive loads of 10 kΩ, the output swings to within a few millivolts of either supply rail,

regardless of the applied power-supply voltage. Different load conditions change the ability of the amplifier to

swing close to the rails. The OPAx607 devices drive up to a nominal capacitive load of 47 pF on the output with

no special consideration and without the need of a series isolation resistor RISO while still being able to achieve

45° of phase margin. When driving capacitive loads greater than 47 pF, TI recommends using RISO as shown in

Figure 8-1 in series with the output as close to the device as possible. Refer to Figure 7-18 for looking up

different values of RISO required for CL to achieve 45° phase margin. Without RISO, the external capacitance (CL)

interacts with the output impedance (ZO) of the amplifier, resulting in stability issues. Inserting RISO isolates CL

from ZO and restores the phase margin. Figure 8-1 shows the test circuit.

VIN

RISO

10 k

VOUT

OPAx607

IOVERLOAD

10mA max

Figure 8-1. Input Current Protection and Driving Capacitive Loads

Figure 8-2 and Figure 8-3 show the phase margin achieved with varying RISO with different values of CL.

RISO (:)

100

150

200

250

300

350

400

450

500

100

D018

10pF

22pF

47pF

0.1nF

1nF

10nF

Gain = 10 V/V,

Cf = 2.5 pF,

RL = 10 kΩ

Figure 8-2. Phase Margin vs. Series Isolation

Resistor

RISO (:)

100

150

200

250

300

350

400

450

500

100

D017

10pF

22pF

47pF

0.1nF

1nF

10nF

Gain = 20 V/V,

Cf = 2.5 pF,

RL = 10 kΩ

Figure 8-3. Phase Margin vs. Series Isolation

Resistor

OPA607, OPA2607

SBOS981F – OCTOBER 2019 – REVISED SEPTEMBER 2020

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