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EL2180CW-T7 Datasheet(PDF) 11 Page - Intersil Corporation |
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EL2180CW-T7 Datasheet(HTML) 11 Page - Intersil Corporation |
11 / 15 page 11 Applications Information Product Description The EL2180, EL2280, and EL2480 are current-feedback operational amplifiers that offer a wide -3dB bandwidth of 250MHz and a low supply current of 3mA per amplifier. All of these products also feature high output current drive. The EL2180 can output 100mA, while the EL2280 and the EL2480 can output 55mA per amplifier. The EL2180, EL2280, and EL2480 work with supply voltages ranging from a single 3V to ±6V, and they are also capable of swinging to within 1V of either supply on the input and the output. Because of their current-feedback topology, the EL2180, EL2280, and EL2480 do not have the normal gain- bandwidth product associated with voltage-feedback operational amplifiers. This allows their -3dB bandwidth to remain relatively constant as closed-loop gain is increased. This combination of high bandwidth and low power, together with aggressive pricing make the EL2180, EL2280, and EL2480 the ideal choice for many low-power/high-bandwidth applications such as portable computing, HDSL, and video processing. For applications where board space is extremely critical, the EL2180 is available in the tiny 5-pin SOT-23 package, which has a footprint 28% the size of an 8-pin SO. The EL2180, EL2280, and EL2480 are each also available in industry standard pinouts in PDIP and SO packages. For single, dual and triple applications with disable, consider the EL2186 (8-pin single), EL2286 (14-pin dual) and EL2386 (16-pin triple). If lower power is required, refer to the EL2170/EL2176 family which provides singles, duals, and quads with 70MHz of bandwidth while consuming 1mA of supply current per amplifier. Power Supply Bypassing and Printed Circuit Board Layout As with any high-frequency device, good printed circuit board layout is necessary for optimum performance. Ground plane construction is highly recommended. Lead lengths should be as short as possible. The power supply pins must be well bypassed to reduce the risk of oscillation. The combination of a 4.7µF tantalum capacitor in parallel with a 0.1µF capacitor has been shown to work well when placed at each supply pin. For good AC performance, parasitic capacitance should be kept to a minimum especially at the inverting input (see the Capacitance at the Inverting Input section). Ground plane construction should be used, but it should be removed from the area near the inverting input to minimize any stray capacitance at that node. Carbon or Metal-Film resistors are acceptable with the Metal-Film resistors giving slightly less peaking and bandwidth because of their additional series inductance. Use of sockets, particularly for the SO package, should be avoided if possible. Sockets add parasitic inductance and capacitance which will result in some additional peaking and overshoot. Capacitance at the Inverting Input Any manufacturer's high-speed voltage- or current-feedback amplifier can be affected by stray capacitance at the inverting input. For inverting gains this parasitic capacitance has little effect because the inverting input is a virtual ground, but for non-inverting gains this capacitance (in conjunction with the feedback and gain resistors) creates a pole in the feedback path of the amplifier. This pole, if low enough in frequency, has the same destabilizing effect as a zero in the forward open-loop response. The use of large value feedback and gain resistors further exacerbates the problem by further lowering the pole frequency. The experienced user with a large amount of PC board layout experience may find in rare cases that the EL2180, EL2280, and EL2480 have less bandwidth than expected. The reduction of feedback resistor values (or the addition of a very small amount of external capacitance at the inverting input, e.g. 0.5pF) will increase bandwidth as desired. Please see the curves for Frequency Response for Various RF and RG, and Frequency Response for Various CIN-. Feedback Resistor Values The EL2180, EL2280, and EL2480 have been designed and specified at gains of +1 and +2 with RF = 750Ω in PDIP and SO packages and RF = 560Ω in SOT23-5 package. These values of feedback resistors give 250MHz of -3dB bandwidth at AV = +1 with about 2.5dB of peaking, and 180MHz of -3dB bandwidth at AV = +2 with about 0.1dB of peaking. The SOT23-5 package is characterized with a smaller value of feedback resistor, for a given bandwidth, to compensate for lower parasitics within both the package itself and the printed circuit board where it will be placed. Since the EL2180, EL2280, and EL2480 are current-feedback amplifiers, it is also possible to change the value of RF to get more bandwidth. As seen in the curve of Frequency Response For Various RF and RG, bandwidth and peaking can be easily modified by varying the value of the feedback resistor. Because the EL2180, EL2280, and EL2480 are current- feedback amplifiers, their gain-bandwidth product is not a constant for different closed-loop gains. This feature actually allows the EL2180, EL2280, and EL2480 to maintain about the same -3dB bandwidth, regardless of closed-loop gain. However, as closed-loop gain is increased, bandwidth decreases slightly while stability increases. Since the loop stability is improving with higher closed-loop gains, it becomes possible to reduce the value of RF below the specified 560 Ω and 750Ω and still retain stability, resulting in only a slight loss of bandwidth with increased closed-loop gain. EL2180, EL2280, EL2480 |
Similar Part No. - EL2180CW-T7 |
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Similar Description - EL2180CW-T7 |
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