EL2260CN データシートの表示（PDF） - Elantec -> Intersil

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EL2260CN

Dual/Quad 130 MHz Current Feedback Amplifiers

Elantec -> Intersil 

EL2260C EL2460C

Dual Quad 130 MHz Current Feedback Amplifiers

Applications Information Contd

maintain almost constant supply current over

temperature so that AC performance is not de-

graded as much over the entire operating temper-

ature range Of course this increase in perform-

ance doesn’t come for free Since the current has

increased supply voltages must be limited so

that maximum power ratings are not exceeded

Each amplifier in the EL2260C EL2460C con-

sume typically 7 5 mA and maximum 10 0 mA

The worst case power in an IC occurs when the

output voltage is at half supply if it can go that

far or its maximum value if it cannot reach

half supply If we assume that the

EL2260C EL2460C is used for double terminated

video cable driving applications (RL e 150X)

and the gain e a2 then the maximum output

voltage is 2V and the average output voltage is

1 4V If we set the two PDmax equations equal to

each other and solve for VS we can get a family

of curves for various packages and conditions ac-

cording to

RL

VS e

(TJMAX b TAMAX)

N iJA

a

(VOUT)2

(2 IS RL) a VOUT

The following curve shows supply voltage (gVS)

vs temperature for the various packages assum-

ing AV e a 2 RL e 150 and VOUT peak e 2V

The curves include worst case conditions (IS e

10 mA and all amplifiers operating at VOUT peak

e 2V)

Supply Voltage vs Ambient Temperature

for All Packages of EL2260C EL2460C

The curves do not include heat removal or forc-

ing air or the simple fact that the package will

probably be attached to a circuit board which

can also provide some form of heat removal

Larger temperature and voltage ranges are possi-

ble with heat removal and forcing air past the

part

Current Limit

The EL2260C EL2460C have internal current

limits that protect the circuit in the event of the

output being shorted to ground This limit is set

at 100 mA nominally and reduces with junction

temperature At a junction temperature of 150 C

the current limits at about 65 mA If any one

output is shorted to ground the power dissipa-

tion could be well over 1W and much greater if

all outputs are shorted Heat removal is required

in order for the EL2260C EL2460C to survive an

indefinite short

Channel to Channel Isolation

Due to careful biasing connections within the in-

ternal circuitry of the EL2260C EL2460C excep-

tionally good channel to channel isolation is ob-

tained Isolation is over 70 dB at video frequen-

cies of 4 MHz and over 65 dB up to 10 MHz The

EL2460C isolation is improved an additional

10 dB up to about 5 MHz for amplifiers A to B

and amplifiers C to D Isolation is improved an-

other 8 dB for amplifiers A to C and amplifiers B

to D See the curve in the Typical Performance

Curves section for more detail

Driving Cables and Capacitive Loads

When used as a cable driver double termination

is always recommended for reflection-free per-

formance For those applications the back termi-

nation series resistor will decouple the EL2260C

and EL2460C from the capacitive cable and allow

extensive capacitive drive However other appli-

cations may have high capacitive loads without

termination resistors In these applications an

additional small value (5X –50X) resistor in se-

ries with the output will eliminate most peaking

The gain resistor RG can be chosen to make up

for the gain loss created by this additional series

resistor at the output

2260 – 14

14

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