8 Detailed Description

8.1 Overview

The BUF634A device is a high-speed, unity-gain, open-loop buffer that can be used in a wide range of

applications requiring large output current drive or large slew rates. The BUF634A can operate on power

supplies ranging from 4.5 V to 36 V and includes an internal output current limiting feature and thermal

shutdown, thereby making the device rugged and easy to use.

The bandwidth of the BUF634A can be adjusted by connecting a resistor between the V– and BW pins. Its

power scaling with bandwidth makes the device suitable for use in portable battery-powered applications. See

the Section 8.4.1 section for a description of the relationship between bandwidth adjustment resistance and the

device –3-dB bandwidth.

The BUF634A can be used in a composite loop (inside the feedback loop of op amps) to increase output current,

eliminate thermal feedback, and improve capacitive load drive. See Figure 9-7 for this circuit. Decoupling the

high-power output current stage from the precision amplifier gives high precision performance by eliminating

thermal effects on input offset of the composite circuit. With a large slew rate of 3750 V/µs, the BUF634A can

quickly reproduce its input signal at its output without adding considerable delay when used in a composite loop.

When used in a composite loop, the outer amplifier controls the circuit precision and distortion performance and

the buffer augments the circuit output current drive capability.

See the Section 8.2 section for a simplified circuit diagram of the open-loop complementary follower design of

the BUF634A.

8.2 Functional Block Diagram

50

BW

V+

V±

Thermal

Shutdown

(1)

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BUF634A

SBOS948D – FEBRUARY 2019 – REVISED SEPTEMBER 2020

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Product Folder Links: BUF634A