Flag

V-

V+

Differential

Amplifier

Voltage

Amplifier

High Current

Output Stage

Thermal

Shutdown and

Flag Output

OPA551, OPA552

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SBOS100B – JULY 1999 – REVISED JANUARY 2016

7 Detailed Description

7.1 Overview

The OPA55x devices are low-cost, laser-trimmed, operational amplifiers that feature outstanding low-level

accuracy coupled with high output swing. High device performance is maintained as these amplifiers swing to the

specified device limits in a wide range of applications. The OPA551 is unity-gain stable while the OPA552 is

optimized for gains of 5 or greater.

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 Thermal Shutdown

Internal thermal shutdown circuitry shuts down the output when the die temperature reaches approximately

160°C and resets when the die has cooled to 140°C. The flag pin can be monitored to determine if shutdown has

occurred. During normal operation, the current source from the flag pin is less than 50 nA. During shutdown, the

flag pin sources 120 µA (typical).

7.3.2 Current Limit

The OPA55x devices are designed with internal current-limiting circuitry that limits the output current to

approximately 380 mA. The current limit varies with increasing junction temperature as shown in (Figure 11).

This feature, in combination with the thermal protection circuitry, provides protection from many types of overload

conditions, including short-circuit to ground.

7.3.3 Input Protection

The OPA55x features internal clamp diodes to protect the inputs when voltages beyond the supply rails are

encountered. However, input current must be limited to 5 mA. In some cases, an external series resistor may be

required. Many input signals are inherently current-limited; therefore, a limiting resistor may not be required.

Consider that a large series resistor, in conjunction with the input capacitance, can affect stability.

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Product Folder Links: OPA551 OPA552