EL2045CN 데이터 시트보기 (PDF) - Elantec -> Intersil

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EL2045CN

Low-Power 100 MHz Gain-of-2 Stable Operational Amplifier

Elantec -> Intersil 

EL2045C

Low-Power 100 MHz Gain-of-2 Stable Operational Amplifier

Applications Information Contd

for video performance in the topology described

above and the results have been included as typi-

cal dG and dP specifications and as typical per-

formance curves In a gain of a2 driving 150X

with standard video test levels at the input the

EL2045C exhibits dG and dP of only 0 02% and

0 07 at NTSC and PAL Because dG and dP can

vary with different DC offsets the video per-

formance of the EL2045C has been characterized

over the entire DC offset range from b0 714V to

a0 714V For more information refer to the

curves of dG and dP vs DC Input Offset

The output drive capability of the EL2045C al-

lows it to drive up to 2 back-terminated loads

with good video performance For more demand-

ing applications such as greater output drive or

better video distortion a number of alternatives

such as the EL2120 EL400 or EL2074 should be

considered

Output Drive Capability

The EL2045C has been designed to drive low im-

pedance loads It can easily drive 6 VPP into a

150X load This high output drive capability

makes the EL2045C an ideal choice for RF IF

and video applications Furthermore the current

drive of the EL2045C remains a minimum of

35 mA at low temperatures The EL2045C is cur-

rent-limited at the output allowing it to with-

stand shorts to ground However power dissipa-

tion with the output shorted can be in excess of

the power-dissipation capabilities of the package

Capacitive Loads

For ease of use the EL2045C has been designed

to drive any capacitive load However the

EL2045C remains stable by automatically reduc-

ing its gain-bandwidth product as capacitive load

increases Therefore for maximum bandwidth

capacitive loads should be reduced as much as

possible or isolated via a series output resistor

(Rs) Similarly coax lines can be driven but best

AC performance is obtained when they are termi-

nated with their characteristic impedance so that

the capacitance of the coaxial cable will not add

to the capacitive load seen by the amplifier Al-

though stable with all capacitive loads some

peaking still occurs as load capacitance increases

A series resistor at the output of the EL2045C

can be used to reduce this peaking and further

improve stability

Printed-Circuit Layout

The EL2045C is well behaved and easy to apply

in most applications However a few simple tech-

niques will help assure rapid high quality results

As with any high-frequency device good PCB

layout is necessary for optimum performance

Ground-plane construction is highly recommend-

ed as is good power supply bypassing A 0 1 mF

ceramic capacitor is recommended for bypassing

both supplies Lead lengths should be as short as

possible and bypass capacitors should be as close

to the device pins as possible For good AC per-

formance parasitic capacitances should be kept

to a minimum at both inputs and at the output

Resistor values should be kept under 5 kX be-

cause of the RC time constants associated with

the parasitic capacitance Metal-film and carbon

resistors are both acceptable use of wire-wound

resistors is not recommended because of their

parasitic inductance Similarly capacitors should

be low-inductance for best performance

The EL2045C Macromodel

This macromodel has been developed to assist

the user in simulating the EL2045C with sur-

rounding circuitry It has been developed for the

PSPICE simulator (copywritten by the Microsim

Corporation) and may need to be rearranged for

other simulators It approximates DC AC and

transient response for resistive loads but does

not accurately model capacitive loading This

model is slightly more complicated than the

models used for low-frequency op-amps but it is

much more accurate for AC analysis

The model does not simulate these characteristics

accurately

noise

settling-time

CMRR

PSRR

non-linearities

temperature effects

manufacturing variations

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