9 Application and Implementation

Note

Information in the following applications sections is not part of the TI component specification, and TI

does not warrant its accuracy or completeness. TI’s customers are responsible for determining

suitability of components for their purposes. Customers should validate and test their design

implementation to confirm system functionality.

9.1 Application Information

Figure 9-1 shows the BUF634A connected as an open-loop buffer. The source impedance and optional input

connected close to the device pins. Capacitor values as low as 0.1 µF assure stable operation in most

applications, but high output current and fast output slewing can demand large current transients from the power

supplies, requiring the use of solid tantalum 10-µF capacitors. High-frequency, open-loop applications benefit

from special bypassing and layout considerations. See the Section 9.1.1 section for more information. If the

BUF634A input is left floating, the device output can swing to either of the supplies based on the input bias

current polarity.

Optiona l conn ection

for wide ba ndwidth ±

See Adju stable Ba ndwidth

section

Figure 9-1. Buffer Connections

9.1.1 High-Frequency Applications

The excellent bandwidth and fast slew rate of the BUF634A are useful in a variety of high-frequency, open-loop

applications. When operated in an open-loop application, printed circuit board (PCB) layout and bypassing

techniques can affect dynamic performance. Figure 9-2 through Figure 9-6 illustrate various application circuit

examples for the BUF634A.

For best results, use a ground-plane-type circuit board layout and bypass the power supplies with 0.1-µF

ceramic chip capacitors at the device pins in parallel with solid tantalum 10-µF capacitors. Source resistance

affects high-frequency peaking, step-response overshoot, and ringing. Best response is usually achieved with a

series input resistor of 25 Ω to 200 Ω, depending on the signal source. Response with some loads (especially

capacitive) can be improved with a resistor of 10 Ω to 150 Ω in series with the output. When driving multiple

device under test (DUT) inputs in automatic test equipment (ATE) testers (large capacitive load), as illustrated in

Figure 9-3, place an isolation resistor at the output of the BUF634A for adequate phase margin and stability.

BUF634A

SBOS948D – FEBRUARY 2019 – REVISED SEPTEMBER 2020

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