9

Applications Information

Product Description

The EL2170, EL2270, and EL2470 are current-feedback

operational amplifiers that offer a wide -3dB bandwidth of

70MHz and a low supply current of 1mA per amplifier. All of

these products also feature high output current drive. The

EL2170 can output 100mA, while the EL2270 and the

EL2470 can output 55mA per amplifier. The EL2170,

EL2270, and EL2470 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 EL2170,

EL2270, and EL2470 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 EL2170, EL2270, and EL2470

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

EL2170 is available in the tiny 5-pin SOT-23 package, which

has a footprint 28% the size of an 8-pin SO. The EL2170,

EL2270, and EL2470 are each also available in industry

standard pinouts in PDIP and SO packages.

For single and dual applications with disable, consider the

EL2176 (8-pin single) and EL2276 (14-pin dual). If higher

speed is required, refer to the EL2180/EL2186 family which

provides singles, duals, triples, and quads with 250MHz of

bandwidth while consuming 3mA 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

14-Pin Plastic DIP

Maximum Power Dissipation

vs Ambient Temperature

14-Pin SO

Maximum Power Dissipation

vs Ambient Temperature

Channel Separation

vs Frequency

5-Pin Plastic SOT-23

Maximum Power Dissipation

vs Ambient Temperature

EL2170, EL2270, EL2470