Beschreibung

The BUF634 is a high-speed, unity-gain, open-loop buffer recommended for a wide range of applications. The BUF634 can be used inside the feedback loop of op amps to increase output current,eliminate thermal feedback, and improve capacitive load drive.
For low-power applications, the BUF634 operates on 1.5mA quiescent current with 250mA output, 2000V/µs slew rate, and 30MHz bandwidth. Bandwidth can be adjusted from 30MHz to 180MHz by connecting a resistor between V– and the BW pin.
Output circuitry is fully protected by internal current limit and thermal shutdown, making the device rugged and easy to use.
The BUF634 is available in a variety of packages to meet mechanical and power-dissipation requirements. Types include SOIC-8 surface-mount, 5-lead TO-220, and a 5-lead TO-263 (DDPAK) surface-mount plastic power packages.

 

Eigenschaften

• A newer version of this device is now available: BUF634A
• High output current: 250mA
• Slew rate: 2000V/µs
• Pin-selected bandwidth: 30MHz to 180MHz
• Low quiescent current: 1.5mA (30MHz BW)
• Wide supply range: ±2.25V to ±18V
• Internal current limit
• Thermal shutdown protection
• Packages:– 5-pin SOIC– 5-pin TO-220– 5-pin TO-263 surface-mount

 

Anwendungen

• Valve driver
• Solenoid driver
• Op amp current booster
• Line driver
• Headphone driver
• Video driver
• Motor driver
• Test equipment
• ATE pin driver

 

Übersicht

The BUF634 device is a high-speed, unity-gain open-loop buffer recommended for a wide range of applications.
The BUF634 can be used inside the feedback loop of op amps to increase output current, eliminate thermal feedback, and improve capacitive load drive.
For low-power applications, the BUF634 operates on 1.5-mA quiescent current with 250-mA output, 2000-V/µs slew rate, and 30-MHz bandwidth. Bandwidth can be adjusted from 30 MHz to 180 MHz by connecting a resistor between V– and the BW pin. Output circuitry is fully protected by internal current limit and thermal shutdown, making this device rugged and easy to use.

 

Merkmal Beschreibung

Output Current

The BUF634 delivers up to ±250-mA continuous output current. Internal circuitry limits output current to approximately ±350 mA. For many applications, however, the continuous output current is limited by thermal effects.
Although all four package types are tested for the same output performance using a high speed test, the higher junction temperatures with the DIP and SO-8 package types often provide less output voltage swing. Junction temperature is reduced in the TO-263 surface-mount power package because this package is soldered directly to the circuit board. The TO-220 package used with a good heat sink further reduces junction temperature, allowing maximum possible output swing.

Funktionsmodi des Geräts

The BUF634 is operational when the power-supply voltage is greater than 4.5 V (±2.25 V). The maximum power supply voltage for the BUF634 is 36 V (±18 V). At low power supply conditions, such as ±2.25 V, the output swing can be limited.

High Frequency Applications

The excellent bandwidth and fast slew rate of the BUF634 device are useful in a variety of high frequency open-loop applications. When operated open-loop, printed-circuit-board layout and bypassing technique can affect dynamic performance.
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.

Detailed Design Procedure

To make sure that the composite amplifier remains stable, the phase shift of the BUF634 must remain small throughout the loop gain of the circuit. For a G = +1 op-amp circuit, the BUF634 must contribute little additional phase shift (approximately 20° or less) at the unity-gain frequency of the op amp. Phase shift is affected by various operating conditions that can affect stability of the op amp.