 |
Zakładka z wyszukiwarką danych komponentów |
|
|
Zakładka z wyszukiwarką danych komponentów |
|
AD842JQ Arkusz danych(PDF) 11 Page - Analog Devices |
|
||||||||||||||||||||||||||||||
AD842JQ Arkusz danych(HTML) 11 Page - Analog Devices |
|
|
11 / 17 page  AD842 Data Sheet GROUNDING AND BYPASSING In designing practical circuits with the AD842, the user must take some special precautions whenever high frequencies are involved. Figure 31. AD842 Settling Demonstrating No Settling Tails Circuits must be built with short interconnect leads. Use large ground planes whenever possible to provide a low resistance, low inductance circuit path; this also minimizes the effects of high frequency coupling. Avoid sockets because the increased interlead capacitance can degrade bandwidth. Use feedback resistors of low enough value to ensure that the time constant formed with the circuit capacitances does not limit the amplifier performance. Resistor values of less than 5 kΩ are recommended. If a larger resistor must be used, a small (<10 pF) feedback capacitor connected in parallel with the feedback resistor, RF, can be used to compensate for these stray capacitances and to optimize the dynamic performance of the amplifier in the particular application. Bypass power supply leads to ground as close as possible to the amplifier pins. A 2.2 μF capacitor in parallel with a 0.1 μF ceramic disk capacitor is recommended. CAPACITIVE LOAD DRIVING ABILITY Like all wideband amplifiers, the AD842 is sensitive to capacitive loading. The AD842 is designed to drive capacitive loads of up to 20 pF without degradation of its rated performance. Capacitive loads of greater than 20 pF decrease the dynamic performance of the device, although instability does not occur unless the load exceeds 100 pF. USING A HEAT SINK The AD842 draws less quiescent power than most precision high speed amplifiers and is specified for operation without a heat sink. However, when driving low impedance loads, the current to the load can be 10 times the quiescent current. This creates a noticeable temperature rise. Use of a small heat sink improves performance. TERMINATED LINE DRIVER The AD842 is optimized for high speed line driver applications. Figure 32 shows the AD842 driving a doubly terminated cable in a gain-of-2 follower configuration. The AD842 maintains a typical slew rate of 375 V/μs, which means it can drive a ±10 V, 6.0 MHz signal, or a ±3 V, 19.9 MHz signal. The termination resistor, RT, minimizes reflections from the far end of the cable when equal to the characteristic impedance of the cable. A back-termination resistor (RBT, also equal to the characteristic impedance of the cable) can be placed between the AD842 output and the cable to damp any stray signals caused by a mismatch between RT and the characteristic impedance of the cable. This configuration results in a cleaner signal. With this circuit, the voltage on the line equals VIN because one half of VOUT is dropped across RBT. The AD842 has a 100 mA minimum output current and, therefore, can drive ±5 V into a 50 Ω cable. Choose the feedback resistors, R1 and R2, carefully. Large value resistors are desirable to limit the amount of current drawn from the amplifier output. Large resistors can cause amplifier instability because the parallel resistance of R1||R2 combines with the input capacitance (typically 2 pF to 5 pF) to create an additional pole. The voltage noise of the AD842 is equivalent to a 5 kΩ resistor; these large resistors can significantly increase the system noise. Resistor values of 1 kΩ or 2 kΩ are recommended. If termination is not used, cables appear as capacitive loads and can be decoupled from the AD842 by a resistor in series with the output. Figure 32. Line Driver Configuration (PDIP) 100% 90% 0% 10% 5mV 2µs OUTPUT: 5V/DIV OUTPUT ERROR: 0.01%/DIV 2.2µF 0.1µF 50Ω OR 75Ω CABLE RT = RBT = CABLE CHARACTERISTIC IMPEDANCE 2.2µF 0.1µF R1 R2 –VS +VS VIN AD842 11 6 10 4 5 4 RT RBT TERMINATION RESISTOR FOR INPUT SIGNAL Rev. F | Page 10 of 16 |
Podobny numer części - AD842JQ |
|
Podobny opis - AD842JQ |
|
|
|
Link URL |
| Polityka prywatności |
| ALLDATASHEET.PL |
| Czy Alldatasheet okazała się pomocna? [ DONATE ] |
O Alldatasheet | Reklama | Kontakt | Polityka prywatności | Linki | Lista producentów 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 |
Polish ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
