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AD830JR-REEL Fiches technique(PDF) 14 Page - Analog Devices |
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AD830JR-REEL Fiches technique(HTML) 14 Page - Analog Devices |
14 / 20 page AD830 Rev. C | Page 14 of 20 Driving Cap Loads The AD830 is capable of driving modest sized capacitive loads while maintaining its rated performance. Several curves of bandwidth versus capacitive load are given in Figure 34 and Figure 37. The AD830 was designed primarily as a low distortion video speed amplifier but with a trade-off, for example, giving up very large capacitive load driving capability. If very large capacitive loads must be driven, the network shown in Figure 32 should be used to ensure stable operation. If the loss of gain caused by the resistor, RS, in series with the load is objectionable, the optional feedback network shown may be added to restore the lost gain. +VS VOUT RS 36.5 Ω *OPTIONAL FEEDBACK NETWORK –VS AD830 1 2 3 4 8 7 6 5 A = 1 GM GM C 0.1µF 0.1µF C1 100pF RS R2 R1 1k Ω INPUT SIGNAL VCM ZCM Figure 32. Circuit for Driving Large Capacitive Loads FREQUENCY (Hz) 3 10k –27 100k 1M 10M 100M ±15V ±5V –24 –21 –18 –15 –12 –9 –6 –3 0 Figure 33. Closed-Loop Response vs. Frequency with 100 pF Load and Series Resistor Compensation SUPPLIES, BYPASSING, AND GROUNDING (FIGURE 34) The AD830 is capable of operating over a wide range of supply voltages, both single and dual supplies. The coupling may be dc or ac, provided the input and output voltages stay within the specified common-mode voltage limits. For dual supplies, the device works from ±4 V to ±16.5 V. Single-supply operation is possible over 8 V to 33 V. It is also possible to operate the part with split-supply voltages, for example, +24 V or −5 V for special applications such as level shifting. The primary constraint is that the total potential between the two supplies does not exceed 33 V. Inclusion of power supply bypassing capacitors is necessary to achieve stable behavior and the specified performance. It is especially important when driving low resistance loads. At minimum, connect a 0.1 μF ceramic capacitor at the supply lead of the AD830 package. In addition, for the best bypassing, it is best to connect a 0.01 μF ceramic capacitor and 4.7 μF tantalum capacitor to the supply lead going to the AD830. 0.1µF 0.01µF VP AND VN VP AND VN 4.7µF LOAD GND LEAD LOAD GND LEAD Figure 34. Supply Decoupling Options The AD830 is designed to be capable of rejecting noise and dissimilar potentials in the ground lines. Therefore, proper care is necessary to realize the benefits of the differential amplification of the part. Separation of the input and output grounds is crucial in rejection of the common-mode noise at the inputs and eliminating any ground drops on the input signal line. For example, connecting the ground of a coaxial cable to the AD830 output common (board ground) could degrade the CMR and also introduce power-down loading on cable grounds. However, it is also necessary as in any electronic system to provide a return path for bias currents back to their original power supply. This is accomplished by providing a connection between the differing grounds through a modest impedance labeled ZCM, for example, 100 Ω. Single-Supply Operation The AD830 is capable of operating in single power supply applications down to a voltage of 8 V, with the generalized connection shown in Figure 35. There is a constraint on the common-mode voltage at the input and output that establishes the range for these voltages. Direct coupling may be used for input and output voltages that lie in these ranges. Any gain network applied needs to be referred to the output common connection or have an appropriate offset voltage. In situations where the signal lies at a common voltage outside the common- mode range of the AD830, direct coupling does not work, so ac coupling should be used. Figure 47 shows how to easily accomplish coupling to the AD830. For single-supply operation where direct coupling is desired, the input and output common- mode curves (Figure 36 and Figure 37) should be used. |
Numéro de pièce similaire - AD830JR-REEL |
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Description similaire - AD830JR-REEL |
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