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OPA818

SBOS940 – MAY 2019

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Copyright © 2019, Texas Instruments Incorporated

7 Detailed Description

7.1 Overview

The OPA818 is a 13 V supply, 2.7 GHz gain-bandwidth product (GBWP), voltage feedback operational amplifier

(op amp) featuring a 2.2nV/

√Hz low noise JFET input stage. The OPA818 is decompensated to be normally

stable in gains

≥ 7 V/V. The decompensated architecture allows for a favorable tradeoff of low quiescent current

for a very high GBWP and low distortion performance in high gain applications. The high voltage capability

high frequency signals such as those often found in optical front-end, test and measurement applications, and

medical systems. The low noise JFET input with pico amperes of bias current makes the device particularly

attractive for high transimpedance gain TIA applications and for test and measurement front-ends. OPA818 also

features power down mode that disables the core amplifier for power savings.

OPA818 is built using TI's proprietary high-voltage high-speed complementary bipolar SiGe process.

7.2 Functional Block Diagram

The OPA818 is a conventional voltage feedback op amp with two high-impedance inputs and a low-impedance

output. Standard amplifier configurations are supported like the two basic configurations shown in Figure 6 and

Figure 6. Noninverting Amplifier

Figure 7. Inverting Amplifier

7.3 Feature Description

7.3.1 Input and ESD Protection

The OPA818 is built using a very high speed complementary bipolar process. The internal junction breakdown

voltages are relatively low for these very small geometry devices. These breakdowns are reflected in the

Absolute Maximum Ratings table. All device pins are protected with internal ESD protection diodes to the power

supplies as shown in Figure 8.

These diodes provide moderate protection to input overdrive voltages beyond the supplies as well. The

protection diodes can typically support 10-mA continuous current. Where higher currents are possible (for

example, in systems with ±12-V supply parts driving into the OPA818), current limiting series resistors should be

added in series with the two inputs to limit the current. Keep these resistor values as low as possible because

high values degrade both noise performance and frequency response. There are no back-to-back ESD diodes

Ratings table.