5kW

1/2

OPA2348

10mA max

+5V

V

IN

V

OUT

I

OVERLOAD

5V

0V

G = +1V/V, V

S = +5V

10µs/div

V

IN

V

OUT

OPA348-Q1, OPA2348-Q1, OPA4348-Q1

SBOS465C – JANUARY 2009 – REVISED JANUARY 2016

www.ti.com

7.3 Feature Description

7.3.1 Operating Voltage

The OPAx348-Q1 op amp is fully specified and ensured for operation from 1.8 V to 5.5 V. In addition, many

specifications apply from –40°C to +125°C. Parameters that vary significantly with operating voltages or

temperature are shown in the Typical Characteristics graphs. Power-supply pins should be bypassed with

0.01-

μF ceramic capacitors.

7.3.2 Rail-to-Rail Input

The input common-mode voltage range of the OPAx348-Q1 family of devices extends 200 mV beyond the supply

rails. This performance is achieved with a complementary input stage: an N-channel input differential pair in

parallel with a P-channel differential pair. The N-channel pair is active for input voltages close to the positive rail,

typically (V+) – 1.3 V to 200 mV above the positive supply. The P-channel pair is on for inputs from 200 mV

below the negative supply to approximately (V+) – 1.3 V. A small transition region exists, typically (V+) – 1.4 V to

(V+) – 1.2 V, in which both pairs are on. This 200-mV transition region can vary up to 300 mV with process

variation. Thus, the transition region (both stages on) can range from (V+) – 1.7 V to (V+) – 1.5 V on the low end,

up to (V+) – 1.1 V to (V+) – 0.9 V on the high end. Within this transition region, PSRR, CMRR, offset voltage,

offset drift, and THD may be degraded compared to device operation outside this region.

7.3.3 Rail-to-Rail Input

The input common-mode range extends from (V–) – 0.2 V to (V+) + 0.2 V. For normal operation, the inputs

should be limited to this range. The absolute maximum input voltage is 500 mV beyond the supplies. Inputs

greater than the input common-mode range but less than the maximum input voltage, while not valid, do not

cause any damage to the op amp. Unlike some other op amps, if the input current is limited, the inputs may go

beyond the power supplies without phase inversion, as shown in Figure 19.

Figure 19. No Phase Inversion with Inputs Greater Than Power-Supply Voltage

Normally, input currents are 0.5 pA. However, large inputs (greater than 500 mV beyond the supply rails) can

cause excessive current to flow in or out of the input pins. Therefore, limiting the input current to less than 10 mA

is important as well as keeping the input voltage below the maximum rating. This limiting is easily accomplished

with an input voltage resistor, as shown in Figure 20.

Figure 20. Input Current Protection for Voltages Exceeding the Supply Voltage

12

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