Datenblatt-Suchmaschine für elektronische Bauteile |
|
AD829AQ Datenblatt(PDF) 11 Page - Analog Devices |
|
AD829AQ Datenblatt(HTML) 11 Page - Analog Devices |
11 / 16 page REV. G AD829 –11– Table I. Component Selection for Shunt Compensation Slew Follower Inverter R1 R2 CL CCOMP Rate –3 dB Small Signal Gain Gain ( )( ) (pF) (pF) (V/ s) Bandwidth (MHz) 1Open 100 0 68 16 66 2–1 1 k 1 k5 25 38 71 5–4 511 2.0 k 1 7 90 76 10 –9 226 2.05 k 0 3 130 65 20 –19 105 2 k 0 0 230 55 25 –24 105 2.49 0 0 230 39 100 –99 20 2 k 0 0 230 7.5 Table I gives the recommended CCOMP and CLEAD values, as well as the corresponding slew rates and bandwidth. The capacitor values were selected to provide a small signal frequency response with less than 1 dB of peaking and less than 10% overshoot. For this table, supply voltages of ±15 V should be used. Figure 9 is a graphical extension of the table that shows the slew rate/gain trade-off for lower closed-loop gains, when using the shunt compensation scheme. NOISE GAIN 100 1 1 100 10 10 10 100 1k SLEW RATE VS = 15V CCOMP Figure 9. Value of CCOMP and Slew Rate vs. Noise Gain Current Feedback Compensation Bipolar, nondegenerated, single pole, and internally compensated amplifiers have their bandwidths defined as fT = 1 2 π r e CCOMP = I 2 π kT q CCOMP where fT is the unity gain bandwidth of the amplifier. I is the collector current of the input transistor. CCOMP is the compensation capacitance. re is the inverse of the transconductance of the input transistors. kT/q approximately equals 26 mV @ 27 °C. Since both fT and slew rate are functions of the same variables, the dynamic behavior of an amplifier is limited. Since Slew Rate = 2I CCOMP then Slew Rate fT = 4 π kT q This shows that the slew rate will be only 0.314 V/ µs for every MHz of bandwidth. The only way to increase slew rate is to increase the fT, and that is difficult because of process limitations. Unfortunately, an amplifier with a bandwidth of 10 MHz can only slew at 3.1 V/ µs, which is barely enough to provide a full power bandwidth of 50 kHz. The AD829 is especially suited to a new form of compensation that allows for the enhancement of both the full power band- width and slew rate of the amplifier. The voltage gain from the inverting input pin to the compensation pin is large; therefore, if a capacitance is inserted between these pins, the amplifier’s bandwidth becomes a function of its feedback resistor and the capacitance. The slew rate of the amplifier is now a function of its internal bias (2I) and the compensation capacitance. Since the closed-loop bandwidth is a function of RF and CCOMP (Figure 10), it is independent of the amplifier closed-loop gain, as shown in Figure 12. To preserve stability, the time constant of RF and CCOMP needs to provide a bandwidth of less than 65 MHz. For example, with CCOMP = 15 pF and RF = 1 k Ω, the small signal bandwidth of the AD829 is 10 MHz. Figure 11 shows that the slew rate is in excess of 60 V/ µs. As shown in Figure 12, the closed-loop bandwidth is constant for gains of –1 to –4; this is a property of current feedback amplifiers. FOR C1 OF CCOMP CCOMP SHOULD NEVER EXCEED 15pF FOR THIS CONNECTION 0pF 15pF <7pF 7pF 50 50 COAX CABLE –VS 0.1 F 0.1 F AD829 RF VOUT R1 +VS VIN RL 1k IN4148 CCOMP C1* *RECOMMENDED VALUE Figure 10. Inverting Amplifier Connection Using Current Feedback Compensation |
Ähnliche Teilenummer - AD829AQ |
|
Ähnliche Beschreibung - AD829AQ |
|
|
Link URL |
Privatsphäre und Datenschutz |
ALLDATASHEETDE.COM |
War ALLDATASHEET hilfreich? [ DONATE ] |
Über Alldatasheet | Werbung | Kontakt | Privatsphäre und Datenschutz | Linktausch | Hersteller 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 |