Electronic Components Datasheet Search |
|
BUF634 Datasheet(PDF) 8 Page - Burr-Brown (TI) |
|
|
BUF634 Datasheet(HTML) 8 Page - Burr-Brown (TI) |
8 / 20 page 8 ® BUF634 the quiescent current to approximately 15mA. Intermediate bandwidths can be set by connecting a resistor in series with the bandwidth control pin—see typical curve "Quiescent Current vs Resistance" for resistor selection. Characteristics of the bandwidth control pin can be seen in the simplified circuit diagram, Figure 1. The rated output current and slew rate are not affected by the bandwidth control, but the current limit value changes slightly. Output voltage swing is somewhat improved in the wide bandwidth mode. The increased quiescent current when in wide bandwidth mode produces greater power dissipation during low output current conditions. This quiescent power is equal to the total supply voltage, (V+) + |(V–)|, times the quiescent current. BOOSTING OP AMP OUTPUT CURRENT The BUF634 can be connected inside the feedback loop of most op amps to increase output current—see Figure 4. When connected inside the feedback loop, the BUF634’s offset voltage and other errors are corrected by the feedback of the op amp. To assure that the op amp remains stable, the BUF634’s phase shift 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 may affect stability of the op amp—see typical Gain and Phase curves. Most general-purpose or precision op amps remain unity- gain stable with the BUF634 connected inside the feedback loop as shown. Large capacitive loads may require the BUF634 to be connected for wide bandwidth for stable operation. High speed or fast-settling op amps generally require the wide bandwidth mode to remain stable and to assure good dynamic performance. To check for stability with an op amp, look for oscillations or excessive ringing on signal pulses with the intended load and worst case condi- tions that affect phase response of the buffer. POWER DISSIPATION Power dissipation depends on power supply voltage, signal and load conditions. With DC signals, power dissipation is equal to the product of output current times the voltage across the conducting output transistor, VS – VO. Power dissipation can be minimized by using the lowest possible power supply voltage necessary to assure the required output voltage swing. For resistive loads, the maximum power dissipation occurs at a DC output voltage of one-half the power supply voltage. Dissipation with AC signals is lower. Application Bulletin AB-039 explains how to calculate or measure power dissi- pation with unusual signals and loads. Any tendency to activate the thermal protection circuit indicates excessive power dissipation or an inadequate heat sink. For reliable operation, junction temperature should be limited to 150 °C, maximum. To estimate the margin of safety in a complete design, increase the ambient tempera- ture until the thermal protection is triggered. The thermal protection should trigger more than 45 °C above the maxi- mum expected ambient condition of your application. INPUT CHARACTERISTICS Internal circuitry is protected with a diode clamp connected from the input to output of the BUF634—see Figure 1. If the output is unable to follow the input within approximately 3V (such as with an output short-circuit), the input will conduct increased current from the input source. This is limited by the internal 200 Ω resistor. If the input source can be dam- aged by this increase in load current, an additional resistor can be connected in series with the input. BANDWIDTH CONTROL PIN The –3dB bandwidth of the BUF634 is approximately 30MHz in the low quiescent current mode (1.5mA typical). To select this mode, leave the bandwidth control pin open (no connec- tion). Bandwidth can be extended to approximately 180MHz by connecting the bandwidth control pin to V–. This increases FIGURE 3. Thermal Resistance vs Circuit Board Copper Area. Circuit Board Copper Area BUF634F Surface Mount Package THERMAL RESISTANCE vs CIRCUIT BOARD COPPER AREA 60 50 40 30 20 10 012345 Copper Area (inches2) BUF634F Surface Mount Package 1oz copper |
Similar Part No. - BUF634 |
|
Similar Description - BUF634 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |